Training the brain with smart games like Mahjong stimulates a specific pattern of neural activity. Repetition of this pattern through training can help create new synapses and neural networks that can reorganize and restore the most weakened or damaged cognitive functions.
The goal of the game is to score as many points as possible by collecting the most valuable combination from a given number of dice, more details about the instructions and play here [麻雀とは？| 麻雀ルール入門・麻雀 役 一覧].