Wiki is a software application hosted on a server 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 cross-links between internal pages on the fly. 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. (Definition of Wiki from http://www.wiki.org/)
Created in 2001, Wikipedia is a multilingual, Web-based free content encyclopedia project. Created by Larry Sanger and Jimmy Wales. (From definition of Wikipedia from http://en.wikipedia.org/) First impression of Wikipedia would be: basic site with a number of pages containing different articles, illustrations and links. But the most important thing is how this material is created and edited – mostly by common users who have all the tools for an easy creation of web pages and tracking changes of content. While creating this site took a lot of work and experience of working with FTP, HTML, CGI, Wiki’s main objective is to give every user a chance to write and edit content, as the user doesn’t have to know how to create web pages. Not just taking part writing comments, but being an author and editor of the Wiki’s articles.
To format text you can use Wiki’s layout, which lets you create correct hypertext even if you don’t know HTML.
To edit articles in Wiki you only have to press one button - edit You don’t need great experience to be able to change articles. Wiki’s layout is quite easy, its main rules that are required to create and edit new material can be learned in couple of minutes. It seems like this permissiveness can lead to a full destruction of materials and becoming a junkyard for spam, but it doesn’t happen, and not because people aren’t trying to spam. Every change that takes place in Wiki is saved since the minute article is created. So at any moment you can compare 2 versions of the same article and see what changes were made, edit page again or just revert back to the original/older version of the article. Restoring damage to Wiki’s content is much easier then actually doing the damage. Plus admin always have a right to block editing of a certain page or allow editing to a certain users only.