A fat is a waxy, oily substance and is essential for good health. Fat has double the amount of calories and so poses a problem to individuals who find it difficult to exercise.
If you break down a fat you break it down into something called a fatty acid and glycerol. Proteins are made up of chains of amino acids and are necessary for your body to build enzymes, antibodies and haemoglobin. When you eat protein, your body breaks the protein down into amino acids and then tries to re-assemble them into other configurations to make other needed proteins for use around the body.
Carbohydrates, fats and protein can all be broken down into smaller units. Each one of those macronutrients can be sub-divided. In the case of proteins, proteins are made up of amino acids. Not all proteins have the eight essential amino acids that the body needs. If you are consuming protein and you miss out the essential ones for long periods of time, you are putting yourself at risk of becoming malnourished.