Wikipedia is a free and open encyclopedia project created in 2001 and written collaboratively by largely anonymous volunteers. As of July 2014, Wikipedia included over 32.3 million articles in 287 languages written by over 47 million registered users and numerous anonymous contributors worldwide. The English Wikipedia alone contains over 4.5 million articles.
See also: About Wikipedia
Wikipedia does not make any claims to the validity of its information. This does not mean that you can't find valuable or accurate information in Wikipedia, but you should be aware that there is no formal peer review process in place for Wikipedia articles. Even articles written by experts or vetted by an informal review process may later be edited inappropriately just before you view them.
You should especially be aware that most medical and legal articles are not written by professionals and may contain inaccurate information. So use Wikipedia at your own risk and do not rely on it without checking independent sources.