Very simply put, a Wiki is a web site where anyone can add a page or edit what's already there. The idea is that simple, but it's incredibly powerful.
If you are one of 100 people actively using a wiki, you can think of yourself as an editor for 99 authors, or an author with 99 editors, or both. Even though everyone works part-time, things get done. When a community of interested people come together to create and edit Wiki pages on a subject, the Wiki quickly becomes an archive of the best knowledge of everyone in that community.
To learn more about Wikis, try WhyWikiWorks and WikiNature. Also, consult the WikiWikiWebFaq. lklk