Concentration is a card game, where a Deck of cards is scattered face-down across a table. Players take turns turning over two cards. If they get a matching pair, they keep them. If not, they return them to their original position face-down. Whoever turns over the most matching pairs in the end wins.
The idea is that players try to remember where and what cards that have already been turned over are and use that to their advantage.
In the Yu-Gi-Oh! universe a number of games have been based on this, including:
- Wikipedia:Concentration (game) More in-depth detail on the real world game.