If you've never heard of poker, then you probably live on an alien planet. Poker is by far the most popular card game on the planet. To play poker, players bet on the the value of their 'hand' or combination of cards in their possession. Bets are placed into a location central to all players, called the 'pot', and it is awarded to the winner at the end of the hand. The winner is determined by who holds the highest valued hand according to an established hierarchy of ranking combinations of cards. A winner can also be established if all other players elect to not match the bet of a player.
There are many different variations of poker, however all of them use the same established hierarchy of ranked hands. The pattern of how a hand unfolds changes depending on the variety. There are basically two different varieties, or patterns of how a hand unfolds, how cards are dealt, and the protocol of how bets are made.
Stud - In this variant, cards are dealt to each player either face up or face down, usually with a round of betting following each round of a card being dealt. The most popular game today in this variant is 7 card stud, deals three cards down and four card up for everyone to see. The player must make the best possible 5 card combination from the 7 cards they were dealt. In some types of stud, players are dealt an incomplete hand face down, while a number of cards are dealt face up to be used by all players as community cards to complete their hand. Texas Hold'em is the most popular version of 7 card stud with community cards.
Draw - A complete hand is dealt to each player face down. After a round of betting, players are allowed to give back a number of cards and are dealt new ones them. This is followed by another round of betting. 5 card draw is the most popular version of poker in this variant.
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.
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.
In casual play, the right to deal a hand typically rotates among the players and is marked by a token called a 'dealer' button (or "buck"). In a casino, a house dealer handles the cards for each hand, but the button (typically a white plastic disk) is rotated clockwise among the players to indicate a nominal dealer to determine the order of betting.
One or more players are usually required to make forced bets, usually either an ante or a blind bet (sometimes both). The dealer shuffles the cards, the player one chair to his right cuts, and the dealer deals the appropriate number of cards to the players one at a time. Cards may be dealt either face-up or face-down, depending on the variant of poker being played. After the initial deal, the first of what may be several betting rounds begins. Between rounds, the players' hands develop in some way, often by being dealt additional cards or replacing cards previously dealt. At the end of each round, all bets are gathered into the central pot.
At any time during a betting round, if one player bets and no opponents choose to "call" (match) the bet and instead "fold", the hand ends immediately, the bettor is awarded the pot, no cards are required to be shown, and the next hand begins. This is what makes bluffing possible. Bluffing is a primary feature of poker, one that distinguishes it from other vying games and from other games that make use of poker hand rankings.
At the end of the last betting round, if more than one player remains, there is a showdown, in which the players reveal their previously hidden cards and evaluate their hands. The player with the best hand according to the poker variant being played wins the pot. A poker hand consists of five cards, but in some variants a player has more than five to choose from.