MediaWiki is the software which powers many websites which serve collaborative projects. The software was originally created to power Wikipedia, and, as it is free software, is now used to power many other sites. As Wikipedia is an extremely high-traffic website, MediaWiki is highly optimized for preformance.
Namespaces in MediaWiki
MediaWiki divides pages into logical subdivisions by means of namespaces, which, in MediaWiki, are denoted by a text string, descriptive of the purpose of the page, followed by a colon, all of which preceeds the title. This yields titles in the form of Namespace:Title. Different properties apply to different namespaces. The only exception to the naming scheme is that of the main namespace, which has no prefix.