This is rather old and I was hoping one of the Cathe experts out there would add to it---anyone can do so for those of you who don't know much about wikis.
This is essentially an encyclopedia that anyone can contribute to although one should have a solid knowledge base for the topic they are writing about. Even if someone doesn't more than likely someone else will come along and edit the entry--that's why I am so surprised that no one has come along to contribute to Cathe's entry.
It's a neat tool for fun topics or even an overview of a topic but not a definitive source for research, should anyone be doing any research. I use wikis (of which Wikiepdia is one of the more famous wikis) in my work as many of my colleagues are scattered throughout the globe It's a great collaborative tool for projects, discussions, etc. http://www.wiki.org/wiki.cgi?WhatIsWiki