Card efficiency in blackjack refers to the ability of the cards in play to contribute positively to a player's or dealer's chances of winning, particularly in terms of maximizing potential gains and minimizing losses. It emphasizes the importance of how effectively the player's hand can utilize the cards dealt, especially in scenarios where certain cards can significantly impact the outcome of the game. For instance, high cards like tens and aces are considered efficient as they improve the chances of hitting a strong total or a blackjack. Conversely, lower-value cards can dilute the effectiveness of a hand. Understanding card efficiency allows players to make more informed decisions about hitting, standing, or doubling down, ultimately influencing their betting strategy and likelihood of success in the game.