Carbohydrates are macronutrients - foods we need to eat in reasonably large quantities. The two other macronutrients are protein and fat. Carbs are easily converted to energy by the body, so they supply most of our energy needs. There are basically two main types of carbohydrate: simple carbs and complex carbs - although this classification of carb-types has been superceded by the Glycemic Index (GI) and Glycemic Load (GL).