Fats and oils are concerted source of energy. Certain percentage of body weight of human being is fat and 20-35% of calories should come from fat. Fats in the diet are essential for good health and are needed for the growth of the body and the processing of vitamins. They make up part of all cells and help to maintain the body temperature. They form fatty tissue around delicate organs to protect them from injury.Chemically fats and oils are trimesters of glycerol and higher fatty acids. They are of animal or plant origin. Desi ghee is animal ghee while vanaspati ghee is vegetable ghee. Fats are solids whole oils are liquids at ordinary temperature. Fats and oils may be saturated or unsaturated.
This video explains some simple tests of oils and fats.