They tend to be solid at room temperature. Fats are typically produced by animals. Oils are built from unsaturated fats. Polyunsaturated fats are oils with many double bonds in their fatty acid chains. Oils have lower melting points than fats, and are liquid at room temperature.
Plants produce oils.
Both fats and oils serve important rols in the storage of chemical energy. A similar lipid group, the phospholipids, is built of glycerol, two fatty acids, a phosphate, and a nitrogen-containing group. They play key roles in the structure of cell membranes. Waxes are important as waterproofing agents. Steroids are complex molecules based on a sterol group.