Poker is a card game in which players place bets on their hands. Minimizing losses with poor hands and maximizing winnings with good ones is the underlying skill of the game. It requires knowledge of probability, psychology, and game theory. It also involves bluffing.

Unlike games such as chess, in which information is fully known before betting takes place, Poker is a game of incomplete information, and players must commit resources before knowing the full facts. As the betting phase progresses, more and more information becomes evident. Still, players never have complete command of all the facts until the hand is completed.

Each player starts the game by placing an initial contribution into the pot, called the ante. Players then take turns revealing their cards and putting more money into the pot if they wish to continue. The player with the best hand wins the pot.

There are hundreds of poker variants, but all have the same basic objective: to make the best five-card hand. A professional poker player must be skilled at extracting signal from noise across many channels, including in-person cues like body language and eye contact, as well as technological channels such as the use of software to build behavioral dossiers on opponents and even to buy records of previous hands.

No one knows for sure how poker came to be, but it is widely believed that it developed from a number of earlier card games. Possible ancient roots include 10th-century Chinese domino games and the 16th-century Persian game As Nas. The game likely emerged in the United States in the early 19th century, popularized by riverboat gamblers and spreading throughout America from there.