Poker is a card game that involves betting between two or more players. It is often considered a gambling game, although it can also be a social activity and a way to pass time. The game is based on a combination of probability, psychology, and game theory. Players must make decisions based on their beliefs about the odds of getting a good hand and about the chances that opponents are bluffing.
In most games, the players each put in a fixed amount of money (the size of this bet varies by game) before they are dealt cards. They can then choose to either call (match the bet of the player to their left) or raise it. Players may also drop out of a hand by putting no chips into the pot or simply dropping out of the betting period completely. If a player drops out of the betting, they forfeit any chip value that they have contributed to the pot so far.
The goal of the game is to win the pot, which consists of all bets placed during a single deal. A player wins the pot by having a high-ranking poker hand or by betting with large amounts of their own money to intimidate other players into calling their bluffs. A game of poker can be played with any number of players, but the ideal number is six or seven. John von Neumann proved that if players bet with their best hands and bluffed at mathematically precise frequencies, they will do no worse than break even in the long run.