Search Engine Basics Glossary SEO & Search Terms Explained
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A · B · C · D · E · F · G · H · I · K · L · M · N · P · Q · R · S · T · U · W · X · Y · Z
A
Algorithm
A set of rules a search engine uses to decide which pages answer a query best and in what order to show them. Google runs thousands of these rules together, not one single formula. Read more on Search Engine Algorithms Explained.
Algorithmic update
A change Google makes to how its ranking systems work, ranging from small daily tweaks to large named releases like a Core Update. Most algorithmic updates aren't announced; the big ones usually are.
Alt text
A short written description attached to an image in a page's code, read aloud by screen readers and used by search engines to understand what the image shows. Good alt text describes the picture; it doesn't stuff in keywords.
AltaVista
An early crawler based search engine launched in 1995, known for being one of the first to index full page text rather than just titles and headings. It was eventually folded into Yahoo in 2003.
Anchor text
The clickable, usually underlined, text in a hyperlink. Search engines use anchor text as a clue about what the linked page is about.
AI Overviews
Google's AI generated summary that can appear above traditional search results, pulling together information from multiple sources into one answer. They've reshaped what a "good ranking" even means since their wider rollout. Read more on AI Overviews Explained.
Answer Engine Optimization (AEO)
The practice of structuring content so AI tools and chat based assistants can pull it out and use it as a direct answer, rather than just optimizing for a traditional list of blue links.
Archie
Widely considered the first internet search tool, built in 1990 to index file names on FTP servers. It predates the web itself, which didn't exist publicly yet.
B
Backlink
A link from another website pointing to yours. Search engines have historically treated backlinks as a vote of confidence, though the weight given to any single link depends on the linking site's own trustworthiness.
Baidu
The dominant search engine in mainland China, where Google has limited availability. Baidu uses its own ranking systems tuned to Chinese language search behavior.
Bing Webmaster Tools
A free service from Microsoft that lets site owners submit sitemaps, check indexing status, and see how Bing crawls their site, similar in purpose to Google Search Console.
Bot
Short for robot, a general term for any automated program that visits web pages. Search engine crawlers, like Googlebot, are one type of bot.
Brand mentions
References to a brand or business name online that aren't necessarily linked. Some evidence suggests search engines weigh unlinked mentions as a trust signal, separate from formal backlinks.
C
Canonical tag
A line of code that tells search engines which version of a page is the "main" one when duplicate or near duplicate versions exist, so ranking signals consolidate onto one URL instead of splitting.
Commercial intent
A type of search intent where the user is comparing options before buying, such as "best running shoes for flat feet." Read more on Search Intent Explained.
Core Update
A broad, named change to Google's main ranking systems, released several times a year, that can shift visibility across many sites and topics at once.
Core Web Vitals
A set of measurements Google uses to judge page experience, covering loading speed, visual stability, and how quickly a page responds to interaction.
Crawl budget
The number of pages a search engine bot is willing and able to crawl on your site within a given time period, shaped by your site's size, speed, and how often content changes.
Crawler based search engine
A search engine that finds and ranks pages automatically using bots, as opposed to a directory built by human editors. Google and Bing are both crawler based.
Crawling
The process of a search engine bot visiting a page and reading its content and links. Crawling happens before indexing, and they're often confused for the same thing; they're not. Read more on How Crawling Works.
D
Deindexed
When a page is removed from a search engine's index, meaning it can no longer appear in search results at all. This can happen through a manual noindex tag, a penalty, or a technical error.
DMOZ (Open Directory Project)
A large, volunteer edited web directory that operated from 1998 to 2017. Unlike crawler based engines, it relied entirely on human submissions and review.
Dogpile
A metasearch engine that pulls results from several other search engines at once and combines them into a single results page.
Domain authority
A third party metric, popularized by Moz, that scores a website's likely ranking strength on a 1 to 100 scale based on its backlink profile. It's not a metric Google itself uses or confirms.
Duplicate content
Identical or near identical content that appears on more than one URL, either within a site or across different sites, which can confuse search engines about which version to rank.
DuckDuckGo
A search engine built around not tracking user search history or personalizing results based on past behavior.
E
E-E-A-T
Stands for Experience, Expertise, Authoritativeness, and Trust. It's a framework from Google's own quality rater guidelines used to evaluate whether content was created by someone with genuine knowledge of the topic.
Ecosia
A search engine that donates a portion of its ad revenue to tree planting projects, built on Bing's search index.
Excite
An early web portal and search engine from the 1990s that combined search with news, email, and other services.
F
Featured snippet
A highlighted answer box that appears at the top of some search results, pulling a short excerpt directly from a ranking page. They've become less prominent in many queries now that AI Overviews answer the same intent.
Freshness
How recently a page was published or meaningfully updated, used by search engines as one signal of relevance for queries where current information matters, like news or product comparisons.
G
Generative Engine Optimization (GEO)
The practice of shaping content so it gets pulled into AI generated answers, such as AI Overviews or chat based search responses, rather than just ranking as a traditional blue link.
Googlebot
Google's own web crawler, the automated program responsible for discovering and reading pages across the web so they can be considered for Google's index.
H
Helpful Content Update (HCU)
A Google system, first introduced in 2022, aimed at reducing the visibility of content written primarily to rank in search rather than to genuinely help a reader.
Human powered directory
A list of websites organized and reviewed by people instead of automated bots. Yahoo Directory and DMOZ are well known examples, both now retired.
I
Indexing
The process of storing a crawled page in a search engine's database so it's eligible to appear in results. A page can be crawled but never indexed, which is one of the most common points of confusion for beginners. Read more on How Indexing Works.
Informational intent
A type of search intent where the user wants to learn something, such as "what does crawling mean." Read more on Search Intent Explained.
Infoseek
An early search engine and web portal from the 1990s, later acquired and absorbed by Disney's Go.com.
K
Keyword
A word or phrase a person types into a search engine to find what they're looking for.
Keyword density
The percentage of times a keyword appears relative to the total word count on a page. Modern search engines care far more about topical coverage than hitting a specific density number.
Knowledge graph
Google's internal database of facts about real world entities, people, places, and things, used to power knowledge panels and answer direct factual queries.
Knowledge panel
An information box, usually on the right side of desktop search results, summarizing facts about a person, place, or organization pulled from the knowledge graph.
L
Long-tail keyword
A longer, more specific search phrase, usually with lower individual search volume but clearer intent, such as "how to check if a page is indexed" instead of just "indexing."
M
Manual action
A penalty applied to a site by a human reviewer at Google, separate from an algorithmic demotion, usually for violating Google's spam policies. Site owners are notified through Search Console.
Meta description
A short summary of a page's content, written in the page's code, that can appear under the title in search results. It doesn't directly affect rankings but can influence whether someone clicks.
Meta title
The title of a page as defined in its code, shown as the clickable headline in search results and in the browser tab.
Metasearch engine
A search engine that doesn't build its own index but instead gathers and combines results from multiple other search engines.
N
Naver
South Korea's leading search engine and web portal, known for its own content platforms alongside traditional search results.
Navigational intent
A type of search intent where the user already knows the specific site or page they want, such as searching "Gmail login."
Noindex tag
A piece of code that tells search engines not to include a specific page in their index, even if they're allowed to crawl it.
P
Page Experience update
A Google ranking change that incorporated Core Web Vitals and other usability signals, like mobile friendliness and secure connections, into how pages are evaluated.
PageRank
The original algorithm Google was built on, created by Larry Page and Sergey Brin, which scored a page's importance based on the quantity and quality of links pointing to it. The visible PageRank toolbar score is gone, but the underlying concept still shapes how links are weighed. Read more on PageRank Then and Now.
People Also Ask (PAA)
A search results feature showing a list of related questions that expand to reveal a short answer when clicked.
People Also Search For (PASF)
A list of related search terms, often shown near the bottom of a results page or after clicking into a result and returning, suggesting other queries on the same topic.
Perplexity
An AI powered answer engine that generates direct responses to queries with cited sources, functioning as an alternative to traditional search for many users.
Q
Query
The actual word or phrase a user types or speaks into a search engine.
R
Ranking
The process of ordering indexed pages by how well they're likely to satisfy a given query, based on hundreds of confirmed and unconfirmed signals. Read more on How Ranking Works.
Relevance
How closely a page's content matches the meaning and intent behind a search query, one of the core factors search engines weigh when ranking results.
S
Search index
The enormous database a search engine builds from crawled pages, used to quickly retrieve and rank results when someone runs a query.
Search intent
The underlying goal behind a search query, typically grouped into informational, navigational, commercial, or transactional categories. Read more on Search Intent Explained.
Semantic search engine
A search engine designed to understand the meaning and relationships between words in a query, rather than just matching exact keywords.
SERP (Search Engine Results Page)
The page a search engine shows after someone runs a query, which can include organic results alongside features like featured snippets, PAA boxes, and AI Overviews.
Short-tail keyword
A brief, broad search phrase, usually one or two words, such as "shoes." High search volume, but the intent behind it is often unclear.
Sitemap (XML sitemap)
A file listing the URLs on a site that the owner wants search engines to be aware of, helping crawlers discover pages that might otherwise be missed. Read more on How Sitemaps Work.
Spam policies
Google's published rules describing manipulative practices, like cloaking, link schemes, and scraped content, that can lead to a page being demoted or removed from search results.
Spider
Another name for a web crawler, the automated program that moves from link to link reading page content.
T
Thin content
Pages that offer little real value to a reader, such as very short articles, doorway pages, or auto generated text with no substance behind it.
Topical authority
The degree to which a site is seen as a trusted, comprehensive source on a specific subject, built through consistent, accurate coverage of related topics over time rather than a single page.
Transactional intent
A type of search intent where the user is ready to take an action, usually a purchase, such as "buy wireless earbuds." Read more on Search Intent Explained.
U
URL discovery
The process by which a search engine finds new URLs to crawl, whether through links, submitted sitemaps, or other signals.
W
Web crawler
See Crawler based search engine and Crawling. The automated software that systematically visits and reads pages across the web.
X
(No glossary terms currently listed under X.)
Y
Yahoo Directory
Yahoo's original human curated web directory, one of the earliest large scale ways people found websites before crawler based search dominated. It was shut down in 2014.
Yandex
The leading search engine in Russia, with its own crawling and ranking systems separate from Google or Bing.
Z
Zero-click search
A search where the user gets their answer directly on the results page, through a featured snippet, knowledge panel, or AI Overview, without clicking through to any website. The share of zero click searches has been rising, though exact figures vary by source and shift often enough that any number here should be read as a snapshot, not a fixed fact.