Tallow, coconut oil, palm kernel oil, palm oil, and other fatty materials used to make soap are of the triglyceride class of lipids. Triglycerides consist primarily of glyceryl esters of fatty acids formed by the reaction of one molecule of glycerol and three molecules of fatty acids. Some other classes of fats and oils that are not triglycerides are also important commercially.  No real chemical distinction exists to support the concept that oil is a liquid and that fat is solidified oil because reversible changes in physical state can occur due to temperature variations.  According to accepted usage, triglycerides of animal origin are usually termed fats, and those from vegetable sources, oils.