While nutrients are substances needed for growth, metabolism, and for other body functions, macronutrients are nutrients that provide calories or energy. The prefix makro is from the Greek and means big or large, used because macronutrients are required in large amounts. There are three broad classes of macro-nutrients: proteins, carbohydrates, and fats.
The main function of macronutrients is to provide energy, counted as calories. While each of the macronutrient provides calories, the amount provided by each varies. Carbohydrate provides four calories per gram, protein also four while fat provides nine. Macronutrients also have specific roles in maintaining the body and contribute to the taste, texture and appearance of foods, which helps to make the diet more varied and enjoyable. (diets.com)
Click each section to learn the role of each macro as well as examples of good proteins, carbs, and fats.