Poker is a card game in which each player bets according to the strength of their hand. The strongest hands are made of 3 matching cards of one rank, 4 of a kind, straight, or flush. Other types of hands include 2 pairs, or a single unmatched card. When a player has a weak hand, they can try to win by bluffing. This involves betting higher than they should on the possibility that their opponent has a strong hand. Good poker players use self-examination and detailed observation of their opponents to develop an optimal strategy for each game. They may even discuss their hands and playing styles with others for a more objective look. They constantly tweak their strategy to ensure that they’re improving.

Professional poker players are experts in extracting signal from a large amount of information, including body language and other players’ bets. This knowledge allows them to exploit their opponents and protect themselves against their own weaknesses. They also have a strong understanding of math, probability and game theory. In addition to being able to read their opponents, they’re skilled at constructing behavioral dossiers and buying or selling records of other players’ hands.

The earliest contemporary references to the game are found in two separate publications published in 1836, one by J. Hildreth, and the other by Joe Cowell, a comic writer. The popularity of poker rose quickly, and by the mid-19th century, it had reached England.