The other two are fats and carbohydrates.
Protein is used by the body to build, maintain, and repair body tissues.
Protein has little direct effect on blood sugar levels. Protein is in all animal foods. It is in plant foods, but in smaller amounts. Some plant foods do have a fair amount of protein in them, such as dried beans and peas such as pinto, kidney or red beans, or lentils and split peas. Plant proteins are lower in fat than animal proteins.