Macronutrients are nutrients that provide energy and are required by the body in relatively large amounts. There are three main types of macronutrients: carbohydrates, proteins, and fats. Carbohydrates are the body's primary source of energy, proteins are essential for building and repairing tissues, and fats are important for energy storage, hormone production, and cell membrane structure. These macronutrients are essential for overall health and proper functioning of the body.