A Web Search Engine is a program designed to help you to find information on the World Wide Web. There are many search engines available on sites such as MSN, Google, Yahoo! and Ask Jeeves.
When you want to search for a particular item, you need to type in a phrase, or specific key words. The search engine then looks these words up in its index and returns a list of references to what it thinks are the best-matching web pages. This list will usually include the document's title and a short summary of the text. Search engines use regularly updated indexes in order to operate efficiently and quickly.
Of course, a list of references is of no use unless they are sorted into some kind of order. Entering the word 'Internet' into a search engine brings up over 880 million results; however, some pages may be more relevant, authoritative, or popular than others. Most search engines use techniques to sort these results, to provide the "best" results first. These techniques will vary widely between search engines, and also change over time as Internet usage changes and new methods evolve.