Poker is a card game played by two or more players. Each player has a chance to win the pot (the sum of all bets) by making the best five-card hand. If more than one player has a good hand, the pot is split among them. Depending on the game, betting occurs at intervals called rounds. During a round, a player may call a bet, raise it, or fold.
Unlike other card games, Poker is usually played with poker chips. Each chip has a different value, and each game requires a certain number of chips to start. Traditionally, a white chip is worth one unit of money, a red chip is worth five whites, and a blue chip is worth 10 whites. This system helps keep track of the amount of money in the pot.
When a player is all-in, they have put all their remaining chips into the pot. There are special rules governing how this happens, depending on the game.
A player can also make an all-in bet with fewer than all their chips. In this case, the player must be willing to put as many chips into the pot as any player that raised before them.
The earliest known form of Poker was played with a 20-card pack that was evenly distributed between four players. There was no draw, and the best hand was a pair of aces or four kings. It is possible that the ace-and-king pair was unbeatable in this form of the game, and it is likely that other forms of Poker existed with similar conditions.