Poker is a card game in which players place chips (representing money) into a pot in turn, betting on the possibility of forming a particular hand. A hand consists of five cards. A high hand ranks higher, and a low one is less likely to win. The highest ranking hand is a Royal Flush, consisting of a King, Jack, Queen, and Ace of the same suit, all in one group (clubs, diamonds, hearts, or spades). Other winning hands include Straights, Four of a Kind, Full Houses, and Three of a Kind.

The first player to bet has the privilege and obligation to place chips into the pot, and every player in turn must either call or raise his stake if he wishes to remain in the hand. A player who chooses to call a bet must place enough additional chips into the pot to equal the total amount staked by the players who have raised before him, or else fold.

Players may also bluff, betting that they have the best hand when they do not, and winning if players holding superior hands do not call their bets. This type of bluffing is especially common in tournament play.

Earlier vying games with similar characteristics to Poker include Belle, Flux and Trente-un (17th and 18th centuries, Germany), Post and Pair (18th century, England and America), Brag (19th century to present), Bouillotte (French, 17th – 19th centuries), and Mus (Spanish). The latter has only limited bearing on the development of Poker.