From WhatIsaWiki (edited):
A Wiki is a collaboratively-edited website. The distinguishing feature of wikis is typically allowing all users to edit any page, with full freedom to edit, change and delete the work of previous authors. Other typical wiki features include:
- Easy creation of links to wiki pages either by joining capitalized words to form WikiWords or surrounding them with special characters, like: [[Free Links]]
- Easy creation of new wiki pages. On many wikis a link to an undefined page is displayed with a question mark (like SampleUndefinedPage?). Click on the "?" link to create the new page. (Note that "SampleUndefinedPage?" is a special demo page—you can't create it.)
- A Recent changes page which lists pages that have been edited recently.
Wikis use revision control to prevent abuse and track changes, so if someone decides to erase one or more pages it is easy to "revert" back to previous good versions of the "erased page".