Namely
Propylene Glycol is an organic compound (Dialcool) made by hydration of propylene oxide. It occurs naturally in sesame seeds and mushrooms. It is used as a humectant, solvent or binder in cosmetic products. It helps other ingredients to penetrate the skin. Propylene Glycol is the main ingredient in electronic cigarettes.
Propanediol (1,3-propanediol) and propylene glycol (1,2-propanediol) share the same empirical formula (C3H8O2), but their molecular structure is different.