The main function of carbohydrates is to provide energy to the body.
Unnecessarily long explanation coming up:
Carbohydrates come in two forms: starches, and sugars. Starches are commonly known as complex carbohydrates, and sugars simple carbohydrates. It's made up of monosaccharides, and glucose. All biological energy comes from glucose, so therefore all our energy comes from carbohydrates. (The other three biological molecules perform other functions)
