Mahjong is a game for four players that originated in China.

It involves skill, strategy, and calculation, as well as luck. Depending on the variation which is played, luck can be anything from a minor to a dominant factor in success. In Asia, mahjong is as popular as gambling or computer games.

The object of the game is to build complete suits - or melds (usually of threes) - from either 13 or 16 tiles. The first person to achieve this goal wins the game. The winning tile completes the player's set of either 14 or 17 tiles.

There are many variations of mahjong. In many places, players often observe one version -- and are either unaware of other variations or claim that different versions are incorrect. Although many variations today differ only by scoring, there are several main variaties:

* Chinese Classical Mahjong is the oldest variety of Mahjong, and was the version introduced to America in the 1920s under various names. It has a small, loyal following in the West, although few play it in Asia.
* Hong Kong Mahjong or Cantonese Mahjong is possibly the most common form of Mahjong, differing in minor scoring details with the Chinese Classical variety.
* Taiwanese Mahjong is the variety prevalent in Taiwan and involves hands of 16 tiles, as opposed to the 13-tile hands in other versions. It also features bonuses for dealers and recurring dealerships, and allows for multiple players to win from a single discard.
* Japanese Mahjong is a standardized form of Mahjong in Japan, found prevalently in video games. In addition to scoring changes, the rules of riichi and dora are unique highlights of Japanese Mahjong.

Source : http://en.wikipedia.org