Warhammer 40,000 is trademarked, copyrighted, and made by Games Workshop: http://www.games-workshop.com/gws/home.jsp

Warhammer 40,000 (informally known as Warhammer 40K, WH40K or simply 40K) is a tabletop miniature wargame produced by Games Workshop, set in a dystopian science-fantasy universe. Warhammer 40,000 was created by Rick Priestley in 1987 as the futuristic companion to Warhammer Fantasy Battle, sharing many game mechanics. Expansions for Warhammer 40,000 are released periodically which give rules for urban, planetary siege and large-scale combat. The game is currently in its sixth edition, which was published at the end of June 2012.
 
Players can assemble and paint individual, 28 millimetre (approximately 1 inch) scale miniature figures that represent futuristic soldiers, creatures and vehicles of war. These figurines are collected to compose squads in armies that can be pitted against those of other players. Each player brings a roughly equal complement of units to a tabletop battlefield with handmade or purchased terrain. The players then decide upon a scenario, ranging from simple skirmishes to complex battles involving defended objectives and reinforcements. The models are physically moved around the table and the actual distance between models plays a role in the outcome of combat. Play is turn-based, with various outcomes determined by tables and the roll of dice. Battles may last anywhere from a half-hour to a whole weekend, and battles may be strung together to form campaigns. Many game and hobby stores host games, and official tournaments are held on a regular basis, such as the Throne of Skulls.
 
Warhammer 40,000's space-fantasy setting spans a vast fictional universe set in the far future of the forty-first millennium. Its various factions and races include the Imperium of Man, a decentralized yet totalitarian interstellar empire that has ruled the vast majority of humanity for millennia, the Orks (similar to Warhammer Fantasy Orcs), the Eldar (similar to Elves in Warhammer Fantasy Battle), and Daemons (very similar in both universes, although the precise natures of their creation and existence vary slightly), among others. The background and playing rules of each faction are covered in the game's rule books and supplemental army 'codexs', along with articles in the Games Workshop magazines, White Dwarf and Imperial Armour. The game's miniatures are produced by Citadel Miniatures and Forge World.

 

The Warhammer 40,000 setting is used for several tabletop games, video games, and works of fiction, including licensed works published by Black Library, a subsidiary of Games Workshop. The events and characters are described below using in-universe tone.

 

Source: http://en.wikipedia.org/wiki/Warhammer_40,000