A search engine is a software program or script available through the Internet that searches documents and files for keywords and returns the results of any files containing those
keywords.
Popular examples of search engines are Google, Yahoo!, and MSN Search. Search engines utilize automated software applications (referred to as robots, bots, or spiders) that travel along
the Web, following links from page to page, site to site. The information gathered by the spiders
is used to create a searchable index of the Web.
A search engine operates in the following order:
1. Web crawling
2. Indexing
3. Searching
Web search engines work by storing information about many web pages, which they retrieve from the HTML markup of the pages. These pages are retrieved by a Web crawler (sometimes also known as a spider) — an automated Web crawler which follows every link on he site.The site owner can exclude specific pages by using robots.txt.
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.
Popular Search Engines
Google is the world's most popular search engine, The table beside shows some of the world's most popular search engines.
