If you are playing blackjack and your first two cards dealt are identical, you have the option to “split” your hand into two hands. To split your hands, simply slide another bet forward equal to your initial bet, and the dealer will separate your cards, thus creating two hands. A word of caution: Some of the more strict casinos will not allow you to touch your cards, so unless you know differently, you can just let the dealer sort your split out for you.
Some hands are better to split than others; for example, don’t try to split pairs. At first they will warn you with a smile, but the next time a burly man in a polyester jacket might approach you, and offer you a personal escort out of the casino. Aren’t casino people nice?