Neverwinter Nights is set in the fantasy world of the Forgotten Realms campaign setting, with the game mechanics based on the Dungeons & Dragons 3rd edition rules. The game engine was designed around an Internet-based model for running a massively multiplayer online game (MMOG), which would allow end users to host game servers. The intent was to create a potentially infinite massively multiplayer game framework. This game was named after the original Neverwinter Nights online game, the first ever graphical massively multiplayer online role-playing game (MMORPG), which operated from 1991 to 1997 on AOL.
The original release of Neverwinter Nights includes the game engine, a game campaign that can be played as single player or in multiplayer mode, and on Windows releases, the Aurora toolset used for creating custom content that would run in the same engine. Three expansion packs were subsequently released for the game: Shadows of Undrentide in June 2003; Hordes of the Underdark in December 2003; and Kingmaker in November 2004. BioWare then began selling premium modules through an online store in late 2004. The game's success led to a sequel, Neverwinter Nights 2, released on October 31, 2006.