[HK_ADS(wikis)]
The following definition is taken from Wikipedia:

From Wikipedia, the free encyclopedia

For other uses, see Wiki (disambiguation).

A wiki (IPA: [ˈwiː.kiː] <wee-kee> or [ˈwɪ.kiː] <wick-ey>^[1]) is a type of website that allows anyone visiting the site to add, remove, or otherwise edit all content, quickly and easily, often without the need for registration. This ease of interaction and operation makes a wiki an effective tool for collaborative writing. The term wiki is a shortened form of wiki wiki which is from the native language of Hawaii (Hawaiian), where it is commonly used as an adjective to denote something "quick" or "fast" (Hawaiian dictionary). The term Wiki can also refer to the collaborative software itself (wiki engine) that facilitates the operation of such a website (see wiki software). In essence, a wiki is nothing more than a simplified system of creating HTML web pages, combined with a system which records and catalogues all revisions, so that at any time, an entry can be reverted to a previous state. A wiki system may also include various tools, designed to provide users with an easy way to monitor the constantly changing state of the wiki as well as a place to discuss and resolve the many inevitable issues, namely, the inherent disagreement over wiki content. Wiki content can also be misleading, as users are bound to add incorrect information to the wiki page. Some wikis will allow completely unrestricted access so that people are able to contribute to the site without necessarily having to undergo a process of 'registration', as had usually been required by various other types of interactive websites such as Internet forums or chat sites. The first wiki, WikiWikiWeb, is named after the "Wiki Wiki" line of Chance RT-52 buses in Honolulu International Airport, Hawaii. It was created in 1994 and installed on the web in 1995 by Ward Cunningham, who also created the Portland Pattern Repository. Wiki is sometimes interpreted as the backronym for "What I know is", which describes the knowledge contribution, storage and exchange function.And another good definition from Ezra Goodnoe of Internet Week:
A wiki is a Web site that can be edited by anybody who is granted permission. In a business environment, that can mean a workgroup, a department, or even the whole company. The people who access the data and documents in a wiki are also the authors of the wiki, making it ideal for information sharing.

While wikis aren't the best tool for discussions or real-time collaboration, they excel as resources for archiving documents and tracking workflow. In addition to Web pages, wikis can link to spreadsheets, Word documents, PowerPoint slides, PDFs – anything that can be displayed in a browser. They can also embed standard communications media such as e-mail and IM. In other words, they let users gather all the information and correspondence pertinent to a project within one central location.

What's more, most wikis are either open source or based on open-source code. Open-source wikis are absolutely free for companies who implement them, and even licensed versions – which include implementation and support – are cheap compared to standard project- or content-management software. (See Wikis In The Business World for a more complete introduction to wikis and whether they're right for your company.)