Wikipedia 

http://en.wikipedia.org

Wikipedia is a multilingual, web-based, free content encyclopedia project. The name Wikipedia is a portmanteau of the words wiki (a type of collaborative website) and encyclopedia. Wikipedia's articles provide links to guide the user to related pages with additional information.

Wikipedia is written collaboratively by volunteers from all around the world. Since its creation in 2001, Wikipedia has grown rapidly into one of the largest reference Web sites. There are more than 75,000 active contributors working on some 8,700,000 articles in more than 250 languages. Every day hundreds of thousands of visitors from around the world make tens of thousands of edits and create thousands of new articles to enhance the knowledge held by the Wikipedia encyclopedia.

Visitors do not need specialised qualifications to contribute, since their primary role is to write articles that cover existing knowledge; this means that people of all ages and cultural and social background can write Wikipedia articles. With rare exceptions, articles can be edited by anyone with access to the Internet, simply by clicking the edit this page link. Anyone is welcome to add information, cross-references or citations, as long as they do so within Wikipedia's editing policies and to an appropriate standard.

Because Wikipedia is an ongoing work to which, in principle, anybody can contribute, it differs from a paper-based reference source in important ways. In particular, older articles tend to be more comprehensive and balanced, while newer articles more frequently contain significant misinformation, unencyclopedic content, or vandalism. Users need to be aware of this to obtain valid information and avoid misinformation that has been recently added and not yet removed.

Wikipedia has been the topic of fierce debate within the educational community, as more and more students turn to the site as a reference.  Proponents point to the fact that, on average, Wikipedia contains no more errors in its content than a standard encyclopedia, but unlike encyclopedias, those errors can be corrected without significant expense or a new edition.  Critics of the site point to its democratic nature as a weakness, noting that Wikipedia's information cannot always be easily verified and its open platform is makes the validity of the information suspect at any given moment.  Without question, Wikipedia presents a wealth of knowledge, but students using it must practice their information literacy skills.

Some text on this page comes from Wikipedia's about page, and is licensed under the terms of the GNU Free Documentation license.