A Wiki is a online document which is composed and edited by a variety of writers. The best known example of a Wiki is Wikipedia the online encyclopedia which people all over the world can contribute to.

Wikis can also be used for online discussion. For example, I participate in a discussion Wiki hosted by the Learning Circuits blog.

Collaborative web documents such as Wikis can be used as forum for ordinary people to share knowledge. The website HowWiki allows anyone to contribute their "how to" knowledge on any subject.