Card counting in Blackjack is a strategy that helps players improve their odds by tracking the ratio of high to low cards remaining in the deck. By assigning values to the cards—positive for low cards, negative for high cards—players keep a running count to determine when the deck is favorable. A positive count suggests more high cards remain, prompting the player to increase their bets, while a negative count indicates a deck with more low cards, leading the player to bet less. While card counting can shift the odds slightly in the player's favor, it is not foolproof and carries risks, as casinos may take measures to counteract it. Despite these challenges, it remains a way for skilled players to gain a small edge over the house.