Triglycerides are esters with three molecules of fatty acids linked to glycerol, an alcohol. They are named according to the components of fatty acid. For instance, tristearin contains three molecules of stearic acid. Triglycerides are lipids.
According to the Encyclopedia Britannica, triglycerides in animals function as depots of energy. In mammals, they are stored in adipose tissue until they are needed, then they are broken down to a molecule of glycerol and three molecules of fatty acid. The glycerol is then combined with albumin, a protein in blood plasma, and carried in the bloodstream. Triglycerides are also used as insulation and padding for organs.