The game some call Memory and others Concentration -- in which we have to remember the location of objects or cards and either match them or find them in sequence -- is one of the oldest and most basic memory games. This game makes use of the sequential memory we normally use to put on underwear and grab our keys before leaving the house every morning, but it also increases our skill at remembering exactly where those things are.
The same memory function in play with Concentration is also what we use when studying vocabulary or other facts with flash cards. The way we play Concentration -- turning up cards, looking at them, and turning them facedown again -- strengthens our memory throughout the game the same way that studying with flashcards does, by providing reinforcement of the information itself, and the promise of reward (progress) when we get the answer right.
As any student can tell you, it's always better to work with the promise of incentive. Not only does it motivate you to keep playing the game and improving, but it also assigns meaning to the fact or card, because you form an emotional attachment to the information it contains -- in this case, winning the game or acing an exam. Without a personal meaning, no single fact or object will remain in your memory for long, which is why incentives are such a powerful study tool.