Face cards each count as 10, Aces count as 1 or 11, all others count at face value. An Ace with any 10, Jack, Queen, or King is a Blackjack. If you have a Blackjack, the dealer pays you one-and-a-half times your bet unless the dealer also has a Blackjack, in which case it's a push and neither wins.
A blackjack is a short, thick stick that is used as a weapon. [US, informal] Police confiscated guns, knives and blackjacks. regional note: in BRIT, use truncheon.