Poker is a card game of chance, skill, and strategy. Players place chips representing money into a pot when it is their turn to act, and the player with the highest-ranking poker hand wins the pot. A poker hand is composed of five cards. The value of a hand is in inverse proportion to its mathematical frequency, meaning that more rare hands are worth less than more common ones. Players may also bluff, betting that they have a high-value hand when they do not.

The rules of poker vary by variant, but the general principles are the same across all forms of the game. A player must always put in some amount of money to play, called a “bet,” unless they choose to check (pass on their turn to act) or raise a bet made by another player, called “raising.” The last player to put in any bet wins the pot.

Professional poker players are experts at extracting signal from noise, and use multiple channels of information to exploit opponents and protect themselves. They use software and other resources to make up for their lack of in-person knowledge of their opponents, including building behavioral dossiers on them and collecting or buying records of their opponents’ hand histories. They also have the ability to read their opponents’ actions, which is called reading tells. In some cases, this information is enough to know when it is safe to fold a bad hand.