Card counting in blackjack is a strategy used to assess the relative composition of the remaining cards in the deck, allowing players to make more informed decisions about their bets and gameplay. The basic principle behind card counting is that high cards (like tens and aces) are advantageous to the player, while low cards benefit the dealer. By keeping a running count of the cards that have been dealt and adjusting bets based on the composition of remaining cards, players attempt to gain an edge over the house. While card counting can improve a player's odds, it requires practice, concentration, and a good memory, as well as an understanding of various card counting systems.