Poker is a card game that involves betting and decisions made on the basis of probability, psychology, and game theory. It can be played by two or more players. Each player puts into the pot a fixed amount of money – called a buy-in. At the beginning of each betting interval, a player may choose to add chips to the pot (called raising) or drop out of the hand altogether (folding). The remaining players then reveal their hands and the player with the highest-ranking poker hand wins the pot. There are several variants of the game, each with its own rules and strategy.
Most poker games are played with poker chips of varying colors and values. The white chip, worth one unit of the ante or bet, is the least valuable; other chips are valued in inverse proportion to their size and color. Players place the chips in front of them on the table. Each player must put a bet into the pot for each round of betting, either by calling it or raising it. A raised bet must match the previous bet and be higher than any prior raises.
In addition to putting in bets, poker players also make bluffs. The success of a bluff depends on the ability of the player to predict whether other players will call their bets. This skill can be improved through mental training techniques, which have been successfully used by many athletes.