Firstly let's look out what a Wiki is

'Wiki is in Ward's original description:
The simplest online database that could possibly work.
Wiki is a piece of server software that allows users to freely create and edit Web page content using any Web browser. Wiki supports hyperlinks and has a simple text syntax for creating new pages and crosslinks between internal pages on the fly.
Wiki is unusual among group communication mechanisms in that it allows the organization of contributions to be edited in addition to the content itself.
Like many simple concepts, "open editing" has some profound and subtle effects on Wiki usage. Allowing everyday users to create and edit any page in a Web site is exciting in that it encourages democratic use of the Web and promotes content composition by nontechnical users.

Historical Note. The first ever wiki site was created for the Portland Pattern Repository in 1995. That site now hosts tens of thousands of pages'. accessed 6/10/09

Wiki's are web 2 technology systems, that allow interactive use, these have develped with intense speeed over the last three years and can be exampled with commonly used and known sites such as: