Blackjack, also known as twenty-one, is the most widely played casino banking game in the world. Blackjack is a comparing card game between a player and dealer, meaning players compete against the dealer but not against other players. It is played with one or more decks of 52 cards. The object of the game is to beat the dealer in one of the following ways:Get 21 points on the player's first two cards (called a blackjack), without a dealer blackjack;Reach a final score higher than the dealer without exceeding 21; orLet the dealer draw additional cards until his or her hand exceeds 21.The player or players are dealt a two-card hand and add together the value of their cards. Face cards (kings, queens, and jacks) are counted as ten points. A player and the dealer can count an ace as 1 point or 11 points. All other cards are counted as the numeric value shown on the card. After receiving their first two cards, players have the option of getting a "hit", or taking an additional card. In a given round, the player or the dealer wins by having a score of 21 or by having the higher score that is less than 21. Scoring higher than 21 (called "busting" or "going bust") results in a loss. A player may win by having any final score equal to or less than 21 if the dealer busts. If a player holds an ace valued as 11, the hand is called "soft", meaning that the player cannot go bust by taking an additional card; 11 plus the value of any other card will always be less than or equal to 21. Otherwise, the hand is "hard".
The dealer must hit until the cards total 17 or more points. (At many tables the dealer also hits on a "soft" 17, i.e. a hand containing an ace and one or more other cards totaling six.) Players win by not busting and having a total higher than the dealer's. The dealer loses by busting or having a lesser hand than the player who has not busted. If the player and dealer have the same total, this is called a "push", and the player typically does not win or lose money on that hand.
If the dealer's upcard is an ace, the player is offered the option of taking "insurance" before the dealer checks the hole card.
Insurance is a side bet that the dealer has blackjack and is treated independently of the main wager. It pays 2:1 (meaning that the player receives two dollars for every dollar bet) and is available when the dealer's exposed card is an ace. The idea is that the dealer's second card has a fairly high probability (nearly one-third) to be ten-valued, giving the dealer blackjack and disappointment for the player. It is attractive (although not necessarily wise) for the player to insure against the possibility of a dealer blackjack by making a maximum "insurance" bet, in which case the "insurance proceeds" will make up for the concomitant loss on the original bet. The player may add up to half the value of their original bet to the insurance and these extra chips are placed on a portion of the table usually marked "Insurance pays 2 to 1".
Players with a blackjack may also take insurance, and in taking maximum insurance they commit themselves to winning an amount exactly equal to their main wager, regardless of the dealer's outcome. Fully insuring a blackjack against blackjack is thus referred to as "taking even money", and paid out immediately, before the dealer's hand is resolved; the players do not need to place more chips for the insurance wager.