A wiki is a collaboration tool - a web site where the pages can be changed and INSTANTLY published using only a web browser (no programming required). Pages are automatically created and linked to each other.
Yet another neat usage for wiki's I discovered at MuttWiki copied below:
This shall be a generic guide for newbies to learn easily the first steps to get things running up to the high end finetuning as seen in some configs of ConfigList & ConfigTricks. We need YOU to build it. Always keep in mind that newbies are supposed to get through this all on their own. This is not a task for experts only! Especially newbies themselves are the best to tell what helped them to get started and how to change the docs to make it easier for the next one reading it. So add what you learn to share it with your comrades in fate who need the help that you can provide.
right on! we should see more of HOWTO's with a wiki backend. they would be so much more comprehensive.
-KunDa (wasnt sure what appropriate wiki page this went to)
see: AboutWiki WhatIsWiki