Poker is a card game in which players make bets against one another, placing them into a central pot. The player with the highest hand wins the pot. The game can be played with any number of cards, though the ideal number is six. The rules vary from game to game, but most forms use the same basic strategy.
The game originated in England around the 1850s. It quickly spread across the world, with major developments in the American Civil War. These included the full 52-card English pack and the introduction of a flush. Other changes included lowball and split-pot games, which differ from the original high-low system.
In most variants of the game, each player places forced bets into a pot before the deal. The players then exchange their cards and place additional bets into the pot as the hand develops. Each round of betting ends when one player has all the cards in their hand, or folds.
The game can be played in a variety of ways, including cash and tournaments. In tournaments, there is often a fixed amount of time for each round. There are also different structures for a tournament, which specify how many rounds should be used and how much money each player is expected to invest in the pot. Some structures are designed to encourage more players to participate, while others limit the total number of competitors. The latter are common in sports and games where each match can only have a small number of competitors, such as most team and racket sports, some combat sports, most card games, and competitive debating.