Poker is a card game involving betting, in which players wager against each other by placing chips (representing money) into the pot. The aim of the game is to have the highest hand at the end of the round, winning the pot. The game is played with a standard 52-card deck, plus any cards specified by the rules of a particular game as wild cards or jokers.
Each player is dealt five cards. The best possible hand is four of a kind, which contains exactly four cards of the same rank. Two identical pairs of cards tie, and the highest card outside breaks ties.
A flush is any five cards of consecutive rank in the same suit. A straight is five cards in sequence but from different suits. Three of a kind is three matching cards of one rank, and a pair is two distinct cards of the same rank. Ties in any of these hands are broken by high card, which is the highest unmatched card in the hand.
Before a hand starts, each player must place an amount of money into the pot, called an ante. Then, each player must call or raise the bet of the person before them in turn. If a player has a good hand, they may bet large quantities, both to improve their chances of a winning hand and as bluffs. John von Neumann proved that a mathematically optimal strategy exists for poker, based on the assumption that players must call or raise large bets with their best hands and bluff only a small percentage of the time with their worst hands.