According to Wikipedia, the world's largest wiki site:
A Wiki ([ˈwiː.kiː] <wee-kee> or [ˈwɪ.kiː] <wick-ey>) is a type of website that allows users to add, remove, or otherwise edit and change most content very quickly and easily.
And that is it! As a part of Wikidot.com network this Site is a customizable piece of the Internet where Users can edit content, upload files, communicate and collaborate.
The thing about Wikis is that it is relatively easy to edit a page or create new pages. Don't worry about mucking the Wiki up. It is also easy to return a page back to an earlier version. You can see the History of any page by selecting that menu option. In this Wiki that menu is at the bottom of every page.