Counting cards is a means by which a blackjack player can change the odds in blackjack in the player’s favor. 
Counting cards is based on that high cards (10 or aces) are better for the player’s expectation than low cards (2,3,4,5,6).
When there are more high cards in the deck, the player will have the chance to receive more blackjacks.
A card counter typically raises his wager size when the deck is rich in high cards.
Card counting is about determining the ratio of high cards to low cards in the deck, and this is done not by memorizing which cards have come out.
