Hot Aisle Containment is a data center cooling strategy designed to improve energy efficiency. It involves enclosing the hot aisles, where servers expel warm air, to prevent this hot air from mixing with the cooler air in the cold aisles. This separation helps maintain optimal temperatures for the equipment. By using physical barriers like walls or curtains, hot air is directed to the cooling units, allowing them to work more effectively. This method not only enhances cooling efficiency but also reduces energy costs, making it a popular choice for modern data centers.