Wikipedia is a free online encyclopedia that is now compared to established reference works. It is based on entries from many free and voluntary contributors, which must be verifiable and created according to specific criteria, and can be critiqued and improved by others. This results in a relatively objective and comprehensive source of information that is accessible to everyone. The only concern is whether the dedicated volunteers will be able to maintain the quality and currency of the rapidly increasing number of articles. At the end of 2009, the millionth German-language Wikipedia entry went online. This book provides an overview of Wikipedia, its founders, its history, and how it works.