Poker is not a single game. Rather, it is a set of gambling card games that share certain traits, such as hand rankings and betting rules. Poker is also one of the few card games that incorporate bluffing into game play, such that it is possible for a player to win a hand entirely by bluffing; especially if they are extremely skilled, very lucky, or both.
There are four main types of poker variants; straight, stud, community, and draw. Straight poker is the oldest and simplest poker game; in straight poker, complete hands are dealt to each player, and all of the players bet in one round. In most straight games, raising -a betting action in which a player puts in more money than the previous player and thus raising the betting amount and forcing all other players to put in the new amount- and re-raising are allowed. Stud poker is when each player is dealt cards face-up and face-down over a number of betting rounds. Face-up cards are often called "streets." In community card poker games, the players are dealt incomplete hands, face-down. Then, a number of cards are dealt face-up to the center of the table, and the players able to complete their hands by taking cards from the center of the table. Community is the most recently developed among the families of poker game variants, having only been around since the 1920s. The most famous among the community card poker games are Omaha Hold'em and Texas Hold'em. Draw poker is a family of poker games where players are dealt complete hands, and they have the option of improving or changing their hands by discarding unwanted cards and having new ones dealt to them, usually face-down.
Generally, the winner of a poker game is determined during the final round of a hand. This last round is called a showdown, and during a showdown, remaining players who are still in contention are required to show their hands. Depending on the poker variant being played, the winning hand can either be the higher hand, the lower hand -which is also often called lowball poker- or there can be a high-low split. A high-low split is when the pot is split between the highest hand, and a low hand that fulfills specific requirements. For example, a low hand that can garner a share of the pot must have all cards with ranks of eight or less.