Card counting in Blackjack involves tracking the ratio of high to low cards remaining in the deck to gain an advantage. By assigning values to cards (positive for low cards, negative for high cards), players keep a running count as the cards are dealt. A high count indicates a favorable deck with more high cards remaining, so players increase their bets. The true count, which adjusts for the number of decks in play, provides a more accurate advantage. Skilled counters may also adjust their playing strategy based on the count. While it can improve a player’s odds, card counting is difficult to do successfully and can lead to being banned by casinos.