PEG/PPG/Polybutylene Glycol-8/5/3 Glycerin
A glycerin derived, synthetic oily liquid that is also water soluble and works as a great skin moisturizer. Its moisturizing ability is comparable to glycerin itself and the two together work in synergy to give skin superb hydration. It is also "cosmetically elegant", i.e. non-sticky and non-greasy.
It can also work as a co-surfactant helping to dissolve small amounts of oily things (think essential oils or vitamin E) into water-based formulas.