The game of Mah-Jong is a version of gin rummy, albeit a little more complex.
It's about grouping tiles (rather than cards) together by suits or sequences.
If you know how to play gin rummy, you're almost there. Mah-Jong is played with four players, rather like a typical number of players for the playing cards equivilent.
A player's goal is to discard and claim tiles to form combinations, until their tiles fit a certain pattern.
Just as with cards, a Mah-Jong player's set of tiles is called a 'hand' and the players take turns to play. Full rules are included in each pack.