For anyone new to Search Engine Optimization (SEO), the language around it can be confusing. Whether you’re learning how search engines work, trying to optimize your own website, or working with an SEO professional, understanding the core vocabulary is essential. This glossary provides simple, clear definitions of the most frequently used SEO terms and concepts. Each definition is written to clarify what the term means, how it’s used, and why it matters.

Algorithm

An algorithm is a set of rules search engines use to determine how pages are ranked in search results. Google’s algorithm (which evolves continuously) evaluates hundreds of ranking factors to decide the order of results based on relevance, authority, and user experience. Algorithm updates (such as Panda, Penguin, and Helpful Content) are released regularly and can significantly affect rankings. See History of Google's Algorithm Updates (brief overview) for more.

Alt Text (Alternative Text)

Alt text is a short, descriptive text added to image tags in HTML. It helps screen readers interpret images for users with visual impairments and allows search engines to understand what the image represents. Well-written alt text improves accessibility and can also enhance image SEO.

Anchor Text

Anchor text is the clickable text in a hyperlink. It helps users and search engines understand the topic of the linked page. Descriptive, relevant anchor text contributes to better SEO and clearer internal linking structure. Avoid generic phrases like “click here” when possible.

Backlink

A backlink is a hyperlink from another website pointing to your site. Backlinks are one of the strongest indicators of a website’s authority. Search engines interpret them as votes of confidence. Earning high-quality backlinks from reputable sources improves rankings. Learn more in Introduction to Off-Page SEO & Link Building.

Bounce Rate

Bounce rate is the percentage of users who leave a website after viewing only one page. While it’s not a direct ranking factor, a high bounce rate may indicate poor content relevance or user experience. Interpreting bounce rate depends on context and intent.

Canonical Tag

A canonical tag is an HTML element that tells search engines which version of a page should be considered the “main” one. It helps avoid duplicate content issues when multiple pages have similar content. For technical implementation, see Canonical Tags & Duplicate Content.

Click-Through Rate (CTR)

CTR is the percentage of users who click on a link after seeing it in search results. A higher CTR often signals that your title and description are compelling and relevant. While CTR is not a direct ranking factor, it can influence performance indirectly.

Crawl / Crawling

Crawling is the process by which search engine bots (also called spiders or crawlers) discover pages across the web by following links. A page must be crawled before it can be indexed. Crawl efficiency is essential for large websites. More in How Search Engines (Like Google) Work.

Crawl Budget

Crawl budget refers to the number of pages a search engine will crawl on your site within a given timeframe. Managing crawl budget is especially important for large websites with thousands of URLs. Factors like site speed, duplicate pages, and server errors can affect crawl efficiency.

Domain Authority

Domain authority (a metric developed by third-party tools like Moz) is an estimate of how likely a website is to rank based on its backlink profile and trust signals. While not used directly by Google, it can be helpful for comparing websites and identifying competitive gaps.

Featured Snippet

A featured snippet is a search result that appears at the top of Google’s organic listings, often in the form of a box with a concise answer. Content optimized for clear, structured answers has a higher chance of being selected as a featured snippet. See Optimizing for Google’s Featured Snippets.

Google Search Console

Google Search Console is a free tool provided by Google that allows you to monitor, maintain, and troubleshoot your website’s presence in search results. It offers insights into indexing, performance, crawl errors, mobile usability, and more. Learn how to use it in Mastering Google Search Console for SEO.

Index / Indexing

An index is the database where search engines store information about discovered web pages. Indexing is the step that follows crawling. A page that’s not indexed cannot appear in search results. Proper indexing is fundamental to visibility.

Internal Link

An internal link connects one page on a website to another page within the same domain. Internal linking helps guide users, distribute page authority, and reinforce site structure. A good internal linking strategy supports both SEO and usability.

Keyword

A keyword is a word or phrase that users type into a search engine. SEO strategies often focus on targeting relevant keywords to align with user search behavior. Keywords should reflect search intent and be used naturally throughout the content. For a full breakdown, see What is Keyword Research (and Why Is It Important?).

Link Building

Link building is the process of acquiring backlinks from other websites. High-quality, relevant backlinks improve a site’s authority and increase its chances of ranking. Effective link building avoids spammy practices and focuses on value and relevance.

Meta Description

A meta description is a brief summary of a page’s content that appears in search results below the title. Although not a direct ranking factor, well-written meta descriptions can improve click-through rates.

Organic Search

Organic search refers to the unpaid search results that appear in search engines based on relevance and authority. SEO aims to improve visibility in organic search results, as opposed to paid listings like PPC ads.

Page Speed

Page speed is how quickly a page loads in a browser. Faster pages provide a better user experience and are favored by search engines. Speed is part of Google’s Core Web Vitals. For optimization, see Core Web Vitals & Page Speed Optimization.

Redirect

A redirect sends users and search engines from one URL to another. A 301 redirect (permanent) passes link equity and is commonly used for URL changes or site migrations. A 302 redirect (temporary) indicates a short-term change.

Robots.txt

The robots.txt file tells search engine crawlers which pages or sections of your site should not be crawled. Misconfigured files can block important content from being indexed. See XML Sitemaps & Robots.txt Guide for more.

Schema Markup

Schema markup is a type of structured data added to your website’s code that helps search engines understand your content. It can enhance your listings with rich results like star ratings, product info, or event details. See Structured Data: Implementing Schema Markup.

SERP (Search Engine Results Page)

SERP refers to the page a search engine displays after a user submits a query. It typically includes organic listings, paid ads, featured snippets, and other result formats depending on the query type.

Sitemap

A sitemap is a file that lists the pages of a website, helping search engines discover and crawl content more efficiently. XML sitemaps are especially useful for large sites or sites with complex navigation.

Title Tag

A title tag is an HTML element that specifies the title of a webpage. It appears as the clickable headline in search results and should be concise, relevant, and optimized for a target keyword.

URL Slug

A URL slug is the part of a URL that identifies a specific page. Clean, descriptive slugs improve readability and SEO. For example, in seoforum.com/base, the slug is base.