When the first two cards you receive are of equal value other than a pair of 4’s, 5’s or 10,s, you may elect to split them and play each as a separate hand, drawing to each until you are satisfied or break. You play the right card first followed by the left card. In many casinos, if a pair is split and a third card of the same rank is drawn, the hand may be re-split. To indicate to the dealer your desire to split, merely slide up another bet of equal value next to your first wager, touching neither your cards not the original bet.
If you are lucky enough to receive a pair of Aces, most casinos only permit drawing one card when two aces are split. When a 10 value card is drawn to an ace that have been split the resulting hands are not blackjacks but are considered 21, this would tie a dealer 21 but lose to a dealer blackjack
If the dealer turns an up-card of an Ace, he will offer “Insurance” to the players. Insurance bets can be made by betting up to half your original bet amount in the insurance betting stripe in front of your bet. The dealer will check to see if he has a 10-value card underneath his Ace, and if he does have Blackjack, your winning Insurance bet will be paid at odds of 2:1. You’ll lose your original bet of course (unless you also have a Blackjack), so the net effect is that you break even (assuming you bet the full half bet for insurance.) This is why the bet is described as “insurance”, since it seems to protect your original bet against a dealer blackjack. Of course, if the dealer does not have blackjack, you’ll lose the insurance bet, and still have to play the original bet out.