A chemically modified version of castor oil that results in a solid, waxy material that serves as an emollient and consistency building material.
It also has some unique moisturizing properties as it is both occlusive and humectant. The former one is common for oils and waxes and it means that it sits on top of the skin hindering water to evaporate out of the top layers. The latter one, the humectant property, is surprising and comes from the unique property of ricinoleic acid (the dominant fatty acid in castor oil) having an extra water-loving -OH group on its otherwise oil-loving fatty chain. We have some more info about this at castor oil, so if you are interested, read on here.