A WikiWikiWeb is a site where everyone can collaborate on the content. One of the most well-known and widely used Wiki is the Portland Pattern Repository at http://c2.com/cgi-bin/wiki?WikiWikiWeb, but recently www.wikipedia.org/ has become almost a synonym for wiki applications.
I found these statements there particularly relevant:
You can say hello on RecentVisitors, or read about HowToUseWiki and AddingPages. Go ahead, join the discussion, play with it, and have fun!