Poker is a card game in which players place bets into a central pot before the cards are dealt. The highest hand wins the pot. The most common hands are three of a kind, straight and flush. Other hands include two pairs, high card and full house. A royal flush is a five-card hand of the same suit (A-K-Q-J-T) and is the best natural hand.
The earliest poker games were based on much earlier European vying games, including Belle, Flux and Trente-un (French, 17th and 18th centuries), Post & Pair (English and French, mid to late 18th century) and Brelan (18th century). The game was developed in the United States during the early 19th century.
There are a variety of different poker formats, but most fall into one of two categories: cash games and tournaments. Cash games involve a fixed amount of money that you place into the pot before each hand. Tournaments are competitions where you compete against other players in a series of matches, with the winner being determined by the number of matches won. These types of competitions are common in a wide range of sports and games, including team and racket sports, combat sports, board games, and competitive debating.
In most cases, people play poker against opponents of relatively similar skill levels. This is known as a relative homogeneous sample, and is also seen in many other sports and games. Whether this is due to players self-selecting into stakes levels on the basis of their own perception of their skill, or because of random chance, it will take a very long time for skill differences to become evident.