Blackjack is a card game and pursues a single goal: either to score 21 points or to end up with a better score than the dealer.
Achieving 21 points from two cards is called "Blackjack" and is paid with 1.5 stakes.
As far as the playing cards' values, the cards between 2 and 10 keep the displayed value, the Ace can be counted as 1 point or 11 points and the cards J, Q, K hold the value of 10 points.
You can find a great variety of Blackjack games, so please visit the payout table and the Help section for more information before entering a game.