Poker is a card game that involves betting among players. It has many variations, but most involve betting in one round and raising and reraising on the basis of probability, psychology, and game theory. The game is played with a pack of cards and chips, with each player taking turns betting. Each player must place at least as much money into the pot as the player to his or her left. If a player chooses not to call, he or she drops out of the hand and forfeits any rights to a later bet. There may be several side pots in addition to the main pot.
In the first betting round the dealer deals three cards face-up on the table, called the flop. These are community cards that everyone can use. Each player can now bet according to his or her perceived strength of the hand. Players with strong hands often raise in order to force weaker players to fold and improve the value of their own hand.
The game has a reputation for being based primarily on chance, but in fact a significant portion of the game is determined by skill and psychology. Some of the best poker players have a gift for reading the other players. This is known as a tell, and it can be subtle, involving eye contact or facial expressions, or more obvious such as gestures. All players have tells and it is possible to spot them if you know what to look for.