Counting cards in blackjack is a way to increase your chances of winning. If you're good at it, you can actually take the odds and put them in your favor. This works because card counters raise their bets when a deck rich in cards that are advantageous to the player comes around. As a general rule of thumb, a deck rich in 10's is better for the player, because the dealer will bust more often, and the player will hit a blackjack more often. Most card counters keep track of the ratio of high car.