What is Search Engine?

Search Engine is a program that searches documents for particular keywords and returns a list of the documents where the keywords were found. Although search engine is truly a general class of programs, the word is often used to particularly describe systems like Alta Vista and Excite that allow users to search for documents on the World Wide Web and USENET newsgroups.

Normally, a search engine works by sending out a spider to get as many documents as possible. Another program, is called an indexer, then reads these documents and creates an index based on the words contained in every document. Each search engine uses a proprietary algorithm to generate its indices such that, preferably, only meaningful results are returned for each query.