Definition of Wikis:

Wiki-wiki is the Hawaiian word for quick.
Wiki websites are designed to enable users to make additions or edit any page of the site. They often have a common vocabulary and consider themselves a "Wiki" community.

Here's a simple introduction to wikis

How to make your own wiki, using wikispaces:

Justine Driver from Bucklands Beach Primary school has resources for maintaining and learning to read on her wiki - - please feel free to use and comment

This wiki is really useful
School Library 2.0 Wiki