Poker is a card game in which players place bets and reveal their cards at the end of the hand to determine the winner. There are many variations of the game, but most involve six or seven players and a single central pot of money. Players must make at least one forced bet, known as an ante or blind, and can then choose to place additional bets in any order they like. Each round of betting involves placing chips into the pot and calling other players’ hands. Depending on the rules of a particular game, cards may be added or removed from hands and the pot size can increase with each bet.
While a significant amount of luck is involved in a poker hand, the long-run expectations of players are determined by their actions. These actions are chosen on the basis of probability, psychology and game theory. The foundational 1944 book by mathematician John von Neumann and economist Oskar Morgenstern, Theory of Games and Economic Behavior, used poker as a primary example of an optimal game and established the principle that bluffing was an essential part of that strategy.
A player can say “call” to indicate he or she wishes to raise the last bet. This must be done prior to the flop, when players can see the community cards that are revealed. This can be helpful to prevent weaker hands from getting too far ahead, and it is also a good way to force players into raising their bets in the event of a strong hand.