Blackjack, also known as 21, is a popular card game played against a dealer. The objective is to have a hand value closer to 21 than the dealer's without exceeding it. Each player is dealt two cards, with face cards worth 10 and Aces valued at either 1 or 11. Players can choose to "hit" for additional cards or "stand" to keep their current total. If a player's hand exceeds 21, they "bust" and lose the round. The game combines strategy and luck, making it a favorite in casinos worldwide.