According to Wikipedia, the world 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 word orginates from Hawii. Wiki means fast, so its basically a fast and efficent web resource - but don't always trust the info, as most people can edit and udate it . :) - posted by Bradmataz