Search Engine is a computer program that retrieves documents or files or data from a database or from a computer network (especially from the internet). Search engines use automated software programs knows as spiders or bots to survey the Web and build their databases. Web documents are retrieved by these programs and analyzed. Data collected from each web page are then added to the search engine index.

When you enter a query at a search engine site, your input is checked against the search engine's index of all the web pages it has analyzed. The best urls are then returned to you as hits, ranked in order with the best results at the top. In short, Search Engine is a program that searches documents for specified keywords and returns a list of the documents where the keywords were found.

Search engine searches for sites based on the words that you designate as search terms. Search engines look through their own databases of information in order to find what it is that you are looking for.

How Search Engines Work

Search engines are the key to finding specific information on the vast expanse of the World Wide Web. When people looking for a search term, the search engine attempts to match this term to categories or keywords in its catalog of World Wide Web sites. The search engine then generates a list of sites that match the search criteria, ranked in order of relevance.

There are basically three types of search engines: Those that are powered by robots (called crawlers; ants or spiders) and those that are powered by human submissions; and those that are a hybrid of the two.

Crawler-based search engines are those that use automated software agents (called crawlers) that visit a Web site, read the information on the actual site, read the site's meta tags and also follow the links that the site connects to performing indexing on all linked Web sites as well. The crawler returns all that information back to a central depository, where the data is indexed. The crawler will periodically return to the sites to check for any information that has changed. The frequency with which this happens is determined by the administrators of the search engine.

Human-powered search engines rely on humans to submit information that is subsequently indexed and catalogued. Only information that is submitted is put into the index.

In both cases, when you query a search engine to locate information, you're actually searching through the index that the search engine has created.


List of the top Internet search engines

ALL THE WEB . GOOGLE . JOEANT . LYCOS .
YAHOO . ALTA VISTA . AOL . ASK JEEVES .
DOGPILE . EXCITE . GIGABLAST . MSN

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