MediaWiki is a free software wiki package, originally for use on Wikipedia. MediaWiki is the particular wiki engine developed for and used by Wikipedia and the other Wikimedia projects. It is freely available for others to use, and there are many copies in use by all sorts of projects around the world.
MediaWiki is an extremely powerful, scalable software and a feature-rich wiki implementation, that uses PHP to process and display data stored in its MySQL database. Pages use MediaWiki’s wikitext format, so that users without knowledge of XHTML or CSS can edit them easily.
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.