If you are new to SEO or planning to hire an SEO agency, this SEO glossary with over 130 important definitions is for you. It breaks down confusing SEO terms into simple, easy-to-understand definitions.

To make things even clearer, we have grouped the terms based on the sequence in which business owners should approach SEO:

• SEO Fundamentals 
• Keyword Research
• Content Creation
• On Page SEO
• Technical SEO
• Off Page SEO
• SEO Performance Tracking

Use this glossary to quickly understand SEO essentials, ask better questions when speaking with SEO agencies, and make smarter, more strategic marketing decisions for your business.

SEO Fundamentals

These are the core concepts and tools every business owner should understand before getting started with SEO or hiring someone to help.

Search Engine Marketing (SEM)

SEM refers to paid advertising on search engines, such as Google. Also known as PPC (Pay Per Click) advertising, SEM is different from SEO, which focuses on getting free (organic) traffic.

Pay Per Click (PPC) Advertising

As mentioned above, PPC advertising refers to ads where you pay search engines when someone clicks. Useful for fast visibility, but unlike SEO, it stops working when your ad spend stops.

Organic Traffic

Visitors who land on your website without clicking on paid search results or paid advertisements. If you neither run PPC advertising with search engines nor spend on social media advertising, all your website traffic is organic traffic. 

Increasing your organic traffic with people interested in your product or service is the main goal of SEO. In other words, you want to attract ideal customer naturally by ranking high for keywords they are searching for.

White Hat SEO

SEO strategies that follow Google’s guidelines, like writing helpful content and earning backlinks naturally. They build long-term trust and rankings.

Black Hat SEO

Black Hat SEO refers to illegal or unethical techniques to try and rank higher on Google. Examples include using hidden text, cloaking, or placing spammy links across the internet pointing to your website. Google penalises websites that use these tactics, which can lead to major ranking drops or even being removed from search results entirely.

Grey Hat SEO

Grey hat SEO refers to tactics that are not clearly against the rules, but that could be risky. These might include publishing AI-generated content with little human input, or link exchanges between unrelated websites.

Crawlability (Crawling)

How easily Google can scan and access your site. If Google cannot crawl your site, it cannot rank it, no matter how good your content is.

Indexing

Once Google crawls your site, it stores (or “indexes”) your pages in its database so they can appear in search results. If a page isn’t indexed, it won’t show up on Google.

GoogleBot

The automated program (also called a “crawler” or “spider”) that Google uses to scan websites and collect information for indexing.

Google Business Profile

Your business listing on Google Maps and local search results. A Google Business Profile is critical for any local business, as it helps people find and contact you.

Google Penalty

When your site drops in rankings due to violating Google’s rules. This can happen manually (by a human reviewer) or automatically (by Google’s algorithm).

Google Webmaster Guidelines

The official rulebook from Google on how to build a website that ranks well and avoids penalties.

Negative SEO

When others try to damage your rankings using harmful SEO tactics, like pointing spammy backlinks to your site or copying your content.

RankBrain

A part of Google’s algorithm that uses AI to understand what people really want to see when they search. It helps Google match searches with the most relevant results.

Ranking Algorithm

The system Google uses to decide which pages appear first in search results. It considers many signals, like content quality, content relevance, backlinks, user experience and much more.

SERP Features

Extra elements on the search results page: like featured snippets, maps, images, star ratings, and “People Also Ask” boxes.

Technical SEO

Behind-the-scenes improvements to help Google read your site better, like fixing speed issues, mobile responsiveness, and crawl problems.

Local SEO

Optimising your website and Google Business Profile, so people in your area can find your business on Google.

International SEO

Helping your website rank in other countries or languages by optimising for location-specific signals and international versions of content.

YouTube SEO

Optimising your YouTube videos to show up in YouTube and Google search, using keywords, tags, viewer engagement signals and more.

Keyword Research

Before you create content or optimize your website, you need to know what your customers are searching for, how many people are searching for them and how strong your competition is. That is what keyword research helps you uncover.

Keyword

A word or phrase someone types into Google.  Example: “yoga mat foldable” is a keyword.

Target Keyword

A keyword that a website page wants to rank for and optimizes its content around. 

Short-Tail Keyword

A broad keyword that someone types into a search engine like Google, that is usually 1 to 2 words long and has high search volume. 

Example: “yoga mat” is a short tail keyword with over 800,000 monthly searches globally. 

Long-Tail Keyword

A very specific keyword that someone types into a search engine like Google, that is usually 3 or more words long and has low search volume. 

Example: “best yoga mat for beginners” is a long tail keyword with approximately 720 monthly searches globally. 

Medium-Tail Keyword

A keyword that falls between a short tail keyword and a long tail keyword, that someone types into a search engine like Google, Medium-tail keywords are usually 3 to 4 words long. 

Example: “yoga mat for beginners” that has approximately 590 searches a month or “yoga mat for travel” that has approximately 9900 searches a month globally. 

Educational Keyword

Search terms (keywords) people use on search engines to learn more about a topic. 

Example: “how to use a yoga mat” is an educational keyword with 320 monthly searches globally. 

Transactional Keyword

Search terms (keywords) people use when they are most likely to make a purchase or book a service. Transactional keywords often have higher competition, as most websites want to attract visitors who are highly likely to purchase. 

Example: “buy running shoes online” or “t-shirt printing Singapore”. While the latter keyword does not include words with purchase intent like “buy”, ”book” or “hire”, it is still a transactional keyword because of the location entered within the search (indicating the searcher is looking to engage a t-shirt printing service provider within Singapore). 

Navigational Keyword

Keywords that are used when someone is trying to find a specific website or brand page. 

Example: “Nike homepage”, “Shopee login”, “Amazon login”.

Branded Keyword

Keywords that include a brand name or name of a competitor.

Example: “Senthil SEO reviews”, “HubSpot pricing”.

Search Intent

The reason behind someone’s search. Are they learning, comparing, or buying? 

Search Volume

Search volume or keyword search volume refers to the number of times a keyword is searched.

Monthly search volume indicates the number of times a keyword is searched on a search engine in a month.

Keyword Difficulty (KD)

An estimate of how competitive a keyword is to rank for. Keywords with lower keyword difficulty (KD) are a lot easier to rank.

Keyword Cannibalisation

When multiple pages on your site compete to rank for the same keyword, it can confuse Google and hurt your website rankings. This is known as keyword cannibalisation. 

This is why keyword research and planning is so important, before you begin creating content on your website.

Keyword Clustering

Grouping related keywords together so that you can target to rank for them in a single, detailed and well-structured page, instead of creating multiple weak pages.

Primary Keyword

The main keyword you want a specific page to rank for. Each page should have just one clear primary keyword.

Secondary Keyword

Supporting keywords that are closely related to your primary keyword and help Google understand your topic more fully.

Related Searches

The suggestions that appear at the bottom of a Google search results page. These are great for finding content ideas and variations of your keyword.

Keyword Stuffing

Unnaturally repeating your keyword too many times in a page to rank for the keyword. This black hat SEO tactic used to work in the late 1990s, but can now hurt your rankings.

Keyword Density

The percentage of times your keyword appears in your content, compared to the total word count. There is no “perfect” number for the right keyword density. The focus needs to be on natural use of keywords instead.

Keyword Stemming

Using different versions or forms of a keyword. 

Example: “run”, “running”, “runner” all stem from the base word “run”.

LSI Keywords (Latent Semantic Indexing Keywords)

Words and phrases related to your topic that help Google understand what your page is really about.

Example: If your keyword is “coffee beans”, LSI terms might include “brewing”, “Arabica”, “grind size”.

Seed Keyword

The starting point of your keyword research, a broad keyword that you can use to generate more keyword ideas. 

Example: As a SEO agency owner, I can use a seed keyword like “SEO”, to generate more keyword ideas like “SEO Agency”, “SEO Agency Singapore”,  “SEO Services’, “SEO Marketing”, “SEO Glossary” and much more. 

Keyword Research Tool

A platform that helps you find new keywords and understand their search volume, competition, intent and more. 

Examples of keyword research tools include Ubersuggest, Ahrefs, Semrush, and Google Keyword Planner.

Keyword Competition

How many other websites are trying to rank for the same keyword?

Highly competitive keywords are harder to rank on Google. Lower competition keywords are easier to rank on Google.

Highly competitive keywords also take a lot longer to rank than lower competition keywords. 

Keyword Profitability

The likelihood that a keyword searched will bring in leads or sales for a business ranking for that keyword. Transactional keywords hold more keyword profitability potential than educational keywords. 

Also, a keyword may have low search volume but still be profitable, if it attracts people who are ready to buy.

Keyword Modifier

A word you add to a base keyword to make it more specific and targeted. Common modifiers include location (“Singapore”), intent (“best”, “affordable”), or action words (“hire”, “buy”).

Example: “photographer” → “affordable wedding photographer Singapore”.

Content Creation

Content creation is at the heart of SEO. It is where you turn keyword research and user intent into helpful, relevant, and engaging content that builds trust, ranks on Google, and converts visitors into customers.

Types of SEO Content

Different formats of content that can help you rank on Google and serve user intent: including blog articles, landing pages, product/service pages, FAQs, how-to guides, videos, infographics, and resource hubs.

Content Strategy

A long-term plan to produce content that aligns with business goals, solves user problems, and ranks in search engines.

Editorial Calendar

Also called a content calendar. A planning tool that outlines what content to publish and when: helping maintain consistency, relevance, and alignment with your overall SEO and marketing strategy.

Content Brief

An outline provided to writers before content creation. It typically includes the target keyword, search intent, structure, tone, and key points to cover.

Content Hub

A central page that links to a group of related articles or subtopics, forming a strong internal linking structure and building topical authority.

Pillar Page

A long-form, in-depth content piece that acts as the foundation for a topic. It links to multiple related subpages or blog posts, creating a collation of related content.

Cornerstone Content

The most valuable, comprehensive content piece on your website. Usually evergreen and designed to establish authority and rank for high-volume keywords.

Supporting Content

Smaller, more targeted content pieces that support your main cornerstone or pillar content. Helps strengthen your overall topic coverage and internal linking.

Skyscraper Content

Skyscraper content is the best and most useful piece of content on a particular topic, because of the depth of the content and the value it adds to your website visitors over what is already out there.

Topical Authority

The level of trust Google gives your website for a specific subject area: built through depth, quality, and quantity of content on that topic.

Content Audit

The process of reviewing all existing content on your site to identify what should be kept, updated, merged, or deleted based on performance and SEO value.

Content Gap Analysis

Identifying content topics that you haven’t written about yet, that you should be writing about based on your industry, niche and SEO goals. You can study your competitors’ content to identify content gaps too. 

Evergreen Content

Content that remains useful and relevant over time without needing frequent updates. Often ideal for long-term organic traffic.

Content Freshness

Refers to how recently content was published or updated. Fresh content can help you rank higher, especially for time-sensitive or trending searches.

Content Relevance

How closely your content matches what the user is searching for in terms of topic, depth, and tone. The more closely you can meet the need of someone searching for a particular keyword in your niche, the more relevant your content is. 

User Intent Match

Ensuring your content actually delivers what the searcher is expecting, whether they are looking for information, a solution, or a product/service.

Content Length

The number of words in a piece of content. Longer content often performs better if it is high-quality, structured well, and genuinely helpful.

SEO-Optimised Content

Content that is created with both users and search engines in mind. SEO optimised content includes clear structure, target keywords, internal links, engaging visuals, and metadata. 

AI-Generated Content

Content created using tools like ChatGPT or Jasper Ai. It should always be reviewed, edited, and fact-checked by humans to maintain quality and avoid duplication. 

E-E-A-T

Google’s quality framework that stands for Experience, Expertise, Authoritativeness, and Trustworthiness. The E-E-A-T framework in SEO is increasingly crucial for ranking well, especially for sensitive or competitive topics.

Duplicate Content

Content that appears on more than one URL, either on the same website or across multiple domains. Can confuse search engines and dilute rankings unless managed properly (e.g. with canonical tags).

Thin Content

Pages with little or no value to the user. Often too short, duplicated, or auto-generated. Google may penalise sites with too much thin content.

Scraped Content

Content copied from other websites without adding original value. Often flagged by Google as spammy or low quality.

On-Page SEO

On-page SEO refers to all the optimisations you can make on your website pages to help them rank higher on Google. It ensures each page is structured, formatted, and written in a way that both users and search engines understand.

Title Tag

The clickable headline that appears on Google search results. Should include your main keyword and stay under 60 characters.

Meta Description

A short summary of your page that appears under the title tag in search results. It doesn’t directly affect rankings but can increase your click-through rate (CTR).

Header Tags (H1, H2, H3, etc.)

Used to break up content and show page structure. H1 is your main heading; use H2s and H3s for subheadings. Helps both users and Google scan your content.

URL Slug

The part of the URL that identifies the specific page. 

Example: https://seowithsenthil.com/blog/simple-seo-glossary/ — 

The slug is simple-seo-glossary. Keep it short, readable, and keyword-focused.

SEO-Friendly URL

A clean, readable URL that includes relevant keywords. Avoid long strings of numbers or symbols in URLs.

Internal Linking

Links between pages on your own website. Helps Google crawl your site and improves user navigation.

External Linking

Links from your content to reputable third-party websites. Used to support facts, data, or references. Choose trustworthy sources.

Alt Text (Image Alt Text)

Descriptive text added to images. Helps with accessibility and tells Google what the image is about. It also helps Google understand and rank images in image search results. 

Image Optimisation

Reducing image file size without losing quality. It helps speed up your website page and improves user experience.

Keyword Placement

Strategically placing your primary keyword (that you want to rank for) in the title, URL, first paragraph, headers, and meta description, without overdoing it.

Content Formatting

Using bullet points, short paragraphs, spacing, and visual elements to make content easier to scan and read.

Jump Links (Anchor Links)

Clickable links that take users to specific sections on the same page. Useful in long-form content to improve navigation and user experience.

Call to Action (CTA)

A prompt that tells readers what to do next — like “Book a call,” “Download guide,” or “Shop now.” Improves conversions by guiding users toward a goal.

Readability

How easy it is for people to read and understand your content. Use plain language, short sentences, and tools like Hemingway Editor or Grammarly to improve it. Good readability increases time spent on page and boosts engagement.

Technical SEO

Technical SEO ensures your website is built in a way that search engines can properly access, interpret, and rank. It is the foundation that supports your content, structure, and visibility on Google.

SSL Certificate

A security protocol that encrypts data between your website and its visitors. It is what gives your site the “HTTPS” label. Google considers HTTPS a trust and ranking signal.

Redirection

A way to send users and search engines from one URL to another when a page is moved, renamed, or removed.

Status Codes

Server responses that tell browsers and search engines what happened with a webpage request:

• 301 (Moved Permanently): Page has been permanently moved.
  
• 302 (Found/Temporary Redirect): Page is temporarily moved.
  
• 304 (Not Modified): Page hasn’t changed since the last visit.
  
• 404 (Not Found): Page no longer exists.
  
• 410 (Gone): Page was intentionally removed.

Canonical URL

Tells Google which version of a page is the primary one when duplicate or similar content exists.

Broken Link

A hyperlink that points to a page that no longer exists. Broken links can harm user experience and reduce SEO trust signals.

Featured Snippet

A summary box that appears at the top of search results for certain queries. Pulled from well-structured, trusted pages, a sign of strong E-E-A-T and technical SEO.

Responsive Website

A site that adjusts automatically to display well on desktop, tablet, and mobile devices. Google prioritises responsive websites through mobile-first indexing.

Mobile-Friendliness

A measure of how easy your website is to use on mobile. Includes layout, font size, tap targets, and responsiveness. Google considers it a ranking factor.

Page Speed

The time it takes for your website to load. Faster pages improve user experience and are more likely to rank better in Google.

Core Web Vitals

A set of performance metrics used by Google to assess user experience:

• LCP (Largest Contentful Paint) – Loading speed
  
• FID (First Input Delay) – Interactivity speed
  
• CLS (Cumulative Layout Shift) – Visual stability during loading

Sitemap

A file (usually in XML format) that lists important pages on your website. Helps search engines discover and crawl content more effectively.

robots.txt

A file that tells search engine bots which areas of your site they are allowed or disallowed from crawling.

Sitelinks

Additional internal links shown in search results below your main listing. Generated by Google for sites with strong authority and clear navigation.

Structured Data (Schema Markup)

Code added to your pages to help search engines understand your content. Can lead to enhanced listings featuring FAQs, reviews, and product details.

Subdomain

A separate section of your main domain (e.g., blog.yoursite.com). Treated as a distinct property by Google in many cases.

Technical SEO Audit

A thorough review of your website’s technical setup, identifying issues that could block search engines or harm rankings. Includes checks on crawlability, indexing, broken links, page speed, mobile-friendliness, and more.

Off Page SEO

Off Page SEO refers to efforts made outside your website to improve your search engine rankings. It is about increasing your website’s reputation, trust, and authority through backlinks and external signals.

Backlink

A hyperlink from another website pointing to yours. It is one of Google’s strongest ranking signals.

High Quality Links

Backlinks from trusted, relevant, and authoritative websites. These help boost your rankings and credibility.

Low Quality Links

Backlinks from spammy, irrelevant, or suspicious websites. These can hurt your rankings or trigger Google penalties.

Link Quality

A measure of how trustworthy and valuable a backlink is. Factors include the linking site’s authority, relevance, content quality, and whether the link appears natural.

Unnatural Links

Links that are paid for, manipulated, or clearly created just to boost rankings. These often violate Google’s guidelines.

Blackhat Link Building

The use of unethical or manipulative tactics to build links, such as link farms, buying shady backlinks, or automated spammy outreach.

Whitehat Link Building

Building backlinks through ethical strategies like outreach, guest posting, digital PR, or creating valuable content people naturally want to reference.

Link Building Strategies

Planned approaches for earning backlinks, such as skyscraper content, broken link building, guest posting, linkable assets, and relationship-based outreach.

Link Building Agency

A service provider that specialises in helping websites get backlinks. Quality varies from agency to agency. Some focus on whitehat SEO, while others may use questionable tactics. Here are 9 best link building agencies around the world. 

Domain Authority (DA)

A metric by Moz SEO tool that predicts a website’s ranking potential. Higher DA generally means stronger trust and backlink profile.

Page Authority (PA)

A Moz score predicting how well a specific page may rank based on links and page structure.

Referring Domain

A unique website that links to your site. Even if it links multiple times, it counts as one referring domain.

Anchor Text

The visible, clickable text in a hyperlink. Descriptive anchor text improves context for search engines.

Nofollow Link

A link with a tag that tells search engines not to pass SEO value. Often used for paid links or user-generated content.

Dofollow Link

A regular link that passes authority. These links have more impact on SEO rankings.

Link Juice

An informal term for SEO value passed through backlinks. Receiving more link juice means more potential for higher rankings.

Toxic Backlink

A harmful link from spammy or suspicious sources. Too many toxic backlinks can negatively affect your website’s SEO.

Spam Score

Another metric by Moz SEO tool estimating how spammy a site may be based on various signals. A higher spam score means higher risk.

Disavow File

A document submitted to Google to ignore certain backlinks that may be harmful to your site.

TrustRank

A concept that search engines use to assess how “trustworthy” your site is based on the quality of backlinks and associations with reputable domains.

Local Link Building

The process of earning backlinks from businesses, directories, media outlets, or community websites in your local area. Crucial for Local SEO success. Here are 15 strategies for local link building that you can use.

SEO Performance Tracking

Learn how to track, evaluate, and optimise your SEO results by analysing the most important metrics, and using tools that can help you monitor them.

SEO Tool

Any online platform or software used to improve your SEO: like keyword research tools (Ubersuggest), analytics platforms (Google Analytics), or powerful all in one SEO platforms (SemRush, Ahrefs etc).

SEO Audit

A full health check of your website to see what is working, what is broken, and where you can improve: across content, links, and technical performance.

Free tools to use: Screaming Frog SEO Spider (free for up to 500 URLs), Ahrefs Webmaster Tools, Google Search Console

Organic Traffic Tracking

Tracking the number of visitors coming from unpaid Google search results (organic search).

Free tool to track organic traffic: Google Analytics

Keyword Rankings

Your site’s position in Google for specific search terms.

Free tool to track keyword rankings: Google Search Console

Click-Through Rate (CTR)

The percentage of people who saw your page in search results and clicked.

Free tools to track: Google Search Console

Bounce Rate

Percentage of visitors who leave your site after viewing one page.

Free tools to track: Google Analytics

Pages per Session

How many pages, on average, a visitor views per visit. Also known as views per session. 

Free tools to track: Google Analytics

Average Session Duration

The average time a user spends on your site during a session.

Free tools to track: Google Analytics

Conversions from Organic Traffic

The number of goal completions (e.g., signups, purchases) from organic visitors.

Free tools to track: Google Analytics, Google Tag Manager

Impressions

How often your pages show up in Google search results.

Free tools to track: Google Search Console

Indexed Pages

The number of your website pages that are indexed and eligible to appear on Google.

Free tools to track: Google Search Console (Coverage report under indexing and then pages,  or using URL Inspection tool)

Crawl Errors

Issues Googlebot faces while trying to access your pages.

Free tools to track: Google Search Console

Core Web Vitals

Google’s 3 key user experience metrics:

• Largest Contentful Paint (LCP)
  
• First Input Delay (FID)
  
• Cumulative Layout Shift (CLS)

Free tools to track: PageSpeed Insights, Google Search Console (Core Web Vitals report), Chrome DevTools, Lighthouse

Page Speed

How fast your page loads for website visitors.

Free tools to track: PageSpeed Insights, GTmetrix (free tier)

Mobile Usability

Checks if your site is mobile-friendly and easy to navigate on phones.

Free tools to track: Google Search Console (Mobile Usability report), Bing Mobile-Friendly Test

Google Search Console (GSC)

A free Google tool that shows how your site performs in search: impressions, clicks, rankings, index status, mobile usability, and more.

Google Analytics (GA)

A free Google tool to study your website metrics, including information such as visitor behavior, traffic sources, bounce rate, and conversions.

These metrics help you measure the performance of your SEO strategy and/or ad campaigns.

Note: GA4 is the latest version as of 2025.