A deck, or pack, is a complete set of playing cards. Casinos use the standard French-suited deck of 52 cards: four suits (spades, hearts, diamonds and clubs), each with 13 ranks running from ace and two through ten to the jack, queen and king. Adding two jokers makes 54 cards, but most casino games leave the jokers out.
Other traditions use their own decks, including Spanish, Italian and German suited packs, as well as stripped decks with some ranks removed and tarot packs for tarot card games. Outside the casino, almost any complete set of cards can be called a deck, whether it is used for games or magic tricks. In blackjack and baccarat, several decks are usually shuffled together and dealt from a shoe.
Why deck count matters
In blackjack, the number of decks is one of the rules that shifts the house edge, alongside dealer rules and payouts. Compare all three when choosing blackjack variants from different providers.