In simple words, Web search engine is a service for finding information on the World Wide Web
Definition- A web search engine is a software system that is designed to search for information on the World Wide Web.
In a search engine, basically these three things happen-
- Web crawling
What is a web crawler- A Web crawler is an Internet bot which systematically browses the World Wide Web, typically for the purpose of Web indexing. A Web crawler may also be called a Web spider, an ant, an automatic indexer or a Web scutter.
What is indexing- Search engine indexing collects, parses, and stores data to facilitate fast and accurate information retrieval. Index design incorporates interdisciplinary concepts from linguistics, cognitive psychology, mathematics, informatics, and computer science. An alternate name for the process in the context of search engines designed to find web pages on the Internet is web indexing.
What is searching- it refers to search engine technology, software for finding information.
How it works
Web search engines work by storing information about web pages, which they retrieve from the HTML markup of the pages. These pages are retrieved by a Web crawler (known as a spider) — an automated Web crawler which follows every link on the site.
The search engine then analyzes the contents of each page to determine how it should be indexed (for example, words can be extracted from the titles, page content, headings, or special fields called meta tags). Data about web pages are stored in an index database for use in later queries. A query from a user can be a single word. The index helps find information relating to the query as quickly as possible.
Some search engines, such as Google, store all or part of the source page (means cache) as well as information about the web pages, whereas others, such as AltaVista, store every word of every page they find.
This is exactly what happens when a user enters a query into a search engine
User enters a query (in general keywords), the engine examines its index and provides a listing of best-matching web pages according to its criteria, usually with a short summary containing the document’s title and sometimes parts of the text. The index is built from the information stored with the data and the method by which the information is indexed.
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