Wikipedia is an open-source encyclopedia, that is maintained by the Wikimedia group. It began with its first edit on 15 January 2001, two days after the domain was registered by Jimmy Wales and Larry Sanger.

Its technological and conceptual underpinnings predate this; the earliest known proposal for an online encyclopedia was made by Rick Gates in 1993, and the concept of a free-as-in-freedom online encyclopedia (as distinct from mere open source) was proposed by Richard Stallman in 1998.

Crucially, Stallman's concept specifically included the idea that no central organization should control editing. This characteristic greatly contrasted with contemporary digital encyclopedias such as Microsoft Encarta, Encyclopedia Britannica, and even Bomis's Nupedia, which was Wikipedia's direct predecessor. 

Wikipedia has helped several organizations and students in getting information about topics around, which was not accessible for free before this. Also, it provided a single source of information about the world.