Search engines help people find relevant information on the Internet.
Major search engines maintain huge databases of web sites that users can search by typing in some text. Each search engine uses its own set of criteria to decide what to include in its database. For example, some search engines index each page in a web site, while others index only the main page. Also unique are the criteria each individual search engine uses to organize information for its users. Other search engines priotitize results according to the summary information contained in sites' meta tags , and still others look for common themes used throughout a site.