Carbohydrates are made up of units of sugar and contain carbon, hydrogen and oxygen. Carbohydrates that contain one sugar unit are monosaccharides eg. glucose or two sugar units are disaccharides eg. sucrose. They are simple sugars.
Some carbohydrates contain many simple sugar units bonded together - these are called polysaccharides eg. starch. They are complex carbohydrates.
Lipids are fats and oils consisting of 3 units of fatty acids joined to a molecule of glycerol.
Proteins are large molecules made from smaller units of amino acids. There are 20 naturally-occurring amino acids, but each molecule has hundreds/thousands of them joined together in a unique sequence and folded into a specific shape, giving each protein individual properties.
Proteins act as structural components of tissues (muscles), hormones, antibodies and enzymes.