Poker is a card game with many variants, played by two or more players. The object is to win the pot, which consists of all bets placed in a deal. Each player is expected to place a small portion of their total stake in each betting round, regardless of whether they have a winning hand. A player may also fold at any time during a betting round.

The game has gained immense popularity in the early 21st century, partly due to the invention of online poker and hole-card cameras, which turned it into a spectator sport that could be broadcast worldwide. The game is often referred to as a “mind game” due to its emphasis on strategic thinking and the psychology of betting patterns.

Despite its long history, it was not until the 20th century that scientific research into poker and other games began to flourish. In the 1930s, John von Neumann wrote his celebrated “Theory of Games” that showed that all kinds of competitive interactions can be modeled mathematically. This led to breakthroughs in areas as diverse as auctions, submarine warfare, and the way species compete for genetic resources.

In a standard poker game, the highest-ranking hands are three of a kind and four of a kind (four cards of the same rank). These beat a flush (3 cards in consecutive ranks of one suit), a straight (5 cards that skip around but are of the same suit), and a full house (2 matching pairs plus an unmatched card). Ties are broken by higher unmatched cards or secondary pairs.