Originally created for Wikipedia, MediaWiki is an open source PHP-based wiki engine now used to run thousands of sites. It is officially classified as a content management system.
Any site that uses MediaWiki as its core software engine is considered a wiki. Wikia wikis are currently running on MediaWiki version 1.19.6.
Features of MediaWiki
MediaWiki is a highly-developed, multi-faceted software that has grown over time to encompass a number of needs for collaborative communities. As such, its features are numerous and usually in flux, but there are some key concepts and tools that MediaWiki is best known for.
An interface that allows for editing of the wiki's content.
Tools that allow for a structured and controlled system of user rights..
Namespaces to help separate and prioritize content.
A platform that allows for easy development of add-ons to the software, known in MediaWiki vernacular as extensions.
A job queue that is designed to help a wiki perform background tasks at a rate that allows for the tasks to be completed in a timely manner without adversely affecting the technical performance of the wiki.
While Wikia runs on the MediaWiki platform, Wikia is not responsible for the development of the core software. Bugs can be reported to Special:Contact and Wikia will try to patch them, though occasionally you may be pointed to MediaWiki's bug-reporting software, Bugzilla if the bug in question is something that comes directly from a core MediaWiki file. You may also place feature requests through Bugzilla.
Wikia develops extensions on the MediaWiki platform and, in the open source spirit that drives MediaWiki, offers them publicly through our SVN and TRAC websites.
However, please be aware that Wikia, due to our unique situation as having to host over 300,000 wikis with a variety of topics and purposes, often optimizes MediaWiki coding for our servers. As such, copying Wikia code from our TRAC or SVN site to a local installation of MediaWiki may prove to be difficult as it will take some rewriting of the code to work on a normal local installation.