Basic Strategy is a set of guidelines used in the game of Blackjack to help players make the best decisions based on their hand and the dealer's upcard. It outlines when to hit, stand, double down, or split pairs, aiming to minimize the house edge and maximize the player's chances of winning. By following Basic Strategy, players can reduce the casino's advantage to as low as 0.5%. This strategy is based on mathematical probabilities and can be found in various charts that players can reference during gameplay, ensuring they make informed choices throughout the game.