Original: Hydrogenation of unsaturated fatty acids is widely practiced to give saturated fatty acids, which are less prone toward rancidification.
Simplified: Fatty acids are aliphatic monocarboxylic acids derived from, or contained in, an animal or vegetable fat, oil, or wax. Natural fatty acids commonly have a chain of four to 28 carbon atoma (usually unbranched and even numbered), which may be saturated or unsaturated.