It is a saturated (no double bonds) hydrocarbon (a molecule consisting only of carbon and hydrogen), meaning that it's a nice and stable oily liquid with a long shelf life. It occurs naturally in certain fish and plant oils (e.g. olive), and in the sebum of the human skin. Squalane's main things are emolliency, surface occlusion, and TEWL prevention all with extreme cosmetic elegance. A superb moisturizer that makes your skin nice and smooth, without being heavy or greasy.