There are many different variations of the game but they are basically a matching tile game. Clear the board by matching the tiles. Some are timed games and others are not.
The Mahjong games available at GSN are Mahjong Dark Dimensions, Mahjong Alchemy, Standard Mahjong, Mahjong Dimensions, Mahjongg Flowers and Mahjong Toy Chest. You can Sign-up for Free at GSN and GameDuell and begin Playing immediately.