Wiki

http://en.wikipedia.org/wiki/Wikipedia:Overview_FAQ

What is Wiki?

Wiki is an excellent collection of interlinked web pages, any of which can be visited and edited by anyone at any time from any place (collaborative software). The concept and software were invented by Ward Cunningham. You could even edit this page by clicking the "edit" link on the third tab above, or edit a section by clicking on "[edit]" to the right, editing only that section. If you don't have anything to add or correct on this page and you just want to see how it works, try out the Wikipedia:Sandbox. See also Wikipedia:Editing FAQ and WikiWiki.

What is Wikipedia?

Wikipedia is a project to produce a new kind of encyclopedia that is comprehensive and free. See Wikipedia:About and the Wikipedia article for even more information.