Fatty acids are of two main types- saturated and unsaturated. Saturated fatty acids are without double bonds in their carbon chains. They have higher melting points and are solids at room temperature. They have a general formula of CnH2nO2, e.g., C16H32O2 (Palmitic acid), C18H36O2 (stearil acid). Animal fats are mostly saturated fats.
Unsaturated fatty acids contain one or more double bonds in their carbon chains. They have lower melting points and are liquids at room temperature. Their general formula is CnH2n2xO2, e.g., oleic acid (with one double bond, monoene, C18H34O2), linoleic acid (with two double bonds, diene, C18H30O2), linolenic acid (with three double bonds, triene, C18H30O2), arachidonic acid (with four double bonds, tetraene, C20H32O2). Plant fats are generally unsaturated fats.