MediaWiki was originally built for Wikipedia.
MediaWiki is a scalable software that uses PHP to process and display data stored in its MySQL database.
Pages on a MediaWiki wiki use MediaWiki's wikitext format, which enables users who have no knowledge of XHTML or CSS to easily edit pages.
According to MediaWiki's description, "When a user submits an edit to a page, MediaWiki writes it to the database, but without deleting the previous versions of the page, thus allowing easy reverts in case of vandalism or spamming. MediaWiki can manage image and multimedia files, too, which are stored in the filesystem. For large wikis with lots of users, MediaWiki supports caching and can be easily coupled with Squid proxy server software.