You and fellow players are dealt two cards each whilst the dealer is dealt one face up. If your first 2 cards add up to 21 (an Ace and a card valued 10), that's Blackjack! If they have any other total, decide whether you wish to 'draw' or 'stay'. You can continue to draw cards until you are happy with your hand.
All cards are at face value, except for the King, Queen and Jack which count as 10. An Ace will have a value of 11 unless that would give a player or the dealer a score in excess of 21; in which case, it has a value of 1.