The one thing that's strange about blackjack is that the rules can be slightly different at each casino and this is the only game where this happens. If you play baccarat, roulette or craps you'll find that the rules are virtually the same at every casino in the U.S. but that isn't the case with blackjack
Atlantic City all of the casinos use 6 or 8 decks of cards that are always dealt from a little rectangular box called a "shoe" and the cards are always dealt face up. In Las Vegas, some casinos will offer that same kind of game while others will offer games that use only 1 or 2 decks that are dealt directly from the dealer's hand and all of the cards will be dealt face down. To make it even stranger, some casinos in Las Vegas will offer both kinds of games in their casinos and the rules will probably change when you move from one table to another.