Polyunsaturated fats [PUFA] are simply fat molecules that have more than one unsaturated carbon bond in the molecule, this is also called a double bond. The best known PUFAs are the omega-3 fatty acids, which include docosahexaenoic acid (commonly known as DHA), but the omega-6 fatty acids are also well known. Polyunsaturated fats must be obtained from foods or supplements, as the body cannot make them from other types of fat. Oils that contain polyunsaturated fats are typically liquid at room temperature but start to turn solid when chilled. Olive oil is an example of a type of oil that contains polyunsaturated fats (Wikipedia).