Wikipedia
Official website: https://en.wikipedia.org (English version)
Introduction
Wikipedia is a collaboratively edited, multilingual, free Internet encyclopedia that is supported by the non-profit Wikimedia Foundation. Volunteers worldwide collaboratively write Wikipedia's 30 million articles in 287 languages, including over 4.4 million in the English Wikipedia.
The logo of Wikipedia, a globe featuring glyphs from several writing systems, most of them meaning the letter w, such as the Arabic 'Wo'. image: wikipedia
Anyone who can access the site can edit almost any of its articles, which on the Internet comprise the largest and most popular general reference work.
In February 2014, The New York Times reported that Wikipedia is ranked fifth globally among all websites stating, "With 18 billion page views and nearly 500 million unique visitors a month..., Wikipedia trails just Yahoo, Facebook, Microsoft and Google, the largest with 1.2 billion unique visitors
Jimmy Wales and Larry Sanger launched Wikipedia on January 15, 2001, the latter creating its name, a portmanteau of wiki (the name of a type of collaborative website, from the Hawaiian word for "quick") and encyclopedia.
source: http://en.wikipedia.org/w/index.php?title=Wikipedia&oldid=603700595