It displays the result of a search engine query from the World Wide Web (www) on a Search Engine Result page (SERP), which is visible to the user.
Search engines are classified into the following categories: 1. Crawler Based Search Engines, 2. Human-powered directories, 3. Hybrid search engine, 4. Meta search Engine.
For crawling and indexing new content, crawler-based search engines use crawlers, bots, or spiders.
Human-powered directories, also known as the open directory system, depend on human-based activities for listings.
Crawlers and manual indexing were used to list the sites in search results. Google uses crawlers as the primary basis and human directories as the secondary basis.
Some search engines, such as Dogpile, use meta-information obtained from other search engines and directories to display their results. These engines are known as "meta-search engines."