The Warhammer World is the Setting of Games Workshops "Warhammer Fantasy" line of games. This includes, amongst others, Warhammer Fantasy Battle, Warhammer Fantasy Roleplay, Warhammer Quest, Mordheim, Man o'War and Blood Bowl.
The Warhammer World is known as the Old World and is bears many geographical and cultural similarities to our own, particularly in and around the Empire, which is very similar to medieval Germany. The medieval tone is garnished with some rennaisance flavour, most notably in the inclusion of firearms and explosive weapons, but also noticeable in clothes. Fantastical elements - including greenskins, chaos, skaven and undead - are added to the mix and have become more prevalent with successive incarnations of the Warhammer Fantasy Battle game.
The overall tone of the setting, at least when focused on the Empire, is grim and gritty, with a tinge of dark humour. Heroism is not necessarily rewarded and corruption is the norm. Magic is a dangerous toy that can bring madness and mutation to its users.
The countryside tends to be perilous, cursed with ravening orcs and insidious ratmen dwell underneath the cities of man, plotting their downfall. The most significant threat comes in the form of the servants of the chaos gods, who at all times seem poised to sweep across the lands. The threat tends to be subtler in the 1st edition of the Roleplaying game, which focuses more on the cultists of these ruinous powers than the more visceral servants, such as daemons and beastmen.
Outside of the Empire, the largely human lands of Bretonnia, Kislev and Estalia serve as approximations of other European countries. Further afield, Lustria takes the role of South America and is peopled by lizardmen. Nagarroth is the home of the dark elves and the island of Ulthuan houses the high elves. Wood elves live in the forests of mortal lands and dwarfs dwell in the mountains. Halflings are less romanticised than in other settings. More than any other humanoid race, they are integrated into human society, but also have their own province in the Empire, known as The Moot.