Concentration or memory is a card game of the Rummy family where all the cards are laid out on a surface and two cards are turned over each turn. The object is to turn over a pair of matching cards (for example, a pair of kings) and then remove them from play. Play ends when all cards have been removed from the table. Optionally, the player who made the match then plays again. Concentration can be played with one player or many players. This scheme is often used in quiz shows.