I think card counting is a well-known strategy used by some players in blackjack. It involves keeping track of the cards that have been played in order to determine when the odds are in the player's favor. Based on this information, the player can vary their bets accordingly and potentially win more mone , casinos do not like when players use this strategy and will often ask them to leave or ban them from playing blackjack altogether. Some casinos also use strategies to prevent card counting, such as using multiple decks of cards or shuffling the cards frequently.