Poker is a family of card games that share betting rules and usually (but not always) hand rankings. Poker games differ in how the cards are dealt, how hands may be formed, whether the high or low hand wins the pot in a showdown (in some games, the pot is split between the high and low hands), limits on bets and how many rounds of betting are allowed. In most modern poker games, the first round of betting begins with some form of forced bet. The action then proceeds to the left. Each player in turn must either match the maximum previous bet or fold, losing all further interest in the hand. A player who matches a bet may also raise, increasing the bet. The betting round ends when all players have either matched the last bet or folded. If all but one player fold on any round, the remaining player collects the pot without showing his hand. If more than one player remains in contention after the final betting round, the hands are shown and the winning hand takes the pot.
Players feel that this betting system distinguishes poker from gambling games. With the minor exception of initial forced bets, money is only placed into the pot voluntarily by a player who, at least in theory, rationally believes the bet has positive expected value. Thus while the outcome of any particular hand is determined mostly by chance, the long-run expectations of the players are determined mostly by their actions chosen based on probability and psychology.
A complete hand is dealt to each player, and players bet in one round, with raising and re-raising allowed. This is the oldest poker family; the root of the game as currently played was a game known as Primero, which evolved into the game three-card brag, a very popular gentleman's game around the time of the American Revolutionary War and still enjoyed in the U.K. today. Straight hands of five cards are sometimes used as a final showdown, but poker is currently virtually always played in a more complex form to allow for additional strategy.Stud
Cards are dealt in a prearranged combination of face-down and face-up rounds, or streets, with a round of betting following each. This is the next-oldest family; as poker progressed from three to five-card hands, they were often dealt one card at a time, either face-down or face-up, with a betting round between each. The most popular stud variant today, seven-card stud, deals two extra cards to each player (three face-down, four face-up) from which they must make the best possible 5-card hand.Draw
A complete hand is dealt to each player, face-down, and after betting, players are allowed to attempt to change their hand (with the object of improving it) by discarding unwanted cards and being dealt new ones. Five-card draw is the most famous variation in this family.Community
A variation of Stud, players are dealt an incomplete hand of face-down cards, and then a number of face-up community cards are dealt to the center of the table, each of which can be used by one or more of the players to make a 5-card hand. Texas hold-em and Omaha are two well-known variants of the Community family.
Other games that use poker hand rankings may likewise be referred to as poker. Video poker is a single-player computer game that functions much like a slot machine; most video poker machines play draw poker, where the player bets, a hand is dealt, and the player can discard and replace cards. Payout is dependent on the hand resulting after the draw and the player's initial bet.
Strip poker is a traditional poker variation where players remove clothing when they lose bets. Since it depends only on the basic mechanic of betting in rounds, strip poker can be played with any form of poker; however, it is usually based on simple variants with few betting rounds, like five card draw.
Another game with the poker name, but with a vastly different mode of play, is called Acey-Deucey or Red Dog poker. This game is more similar to Blackjack in its layout and betting; each player bets against the house, and then is dealt two cards. For the player to win, the third card dealt (after an opportunity to raise the bet) must have a value in between the first two. Payout is based on the odds that this is possible, based on the difference in values of the first two cards. Other poker-like games played at casinos against the house include three card poker and pai gow poker.