Search engine (SE)

A program that searches through all the files on the world wide web, categorizing them by keyword and storing them in a database. When a user enters a keyword, the search engine displays the files that are considered relevant for that keyword.

Google, Bing, Baidu, DuckDuckGo, Yandex, Yahoo, Ask.com, WolframAlpha, and AOL.com are currently the most used search engines.