When formulating our creams and lotions, we carefully consider the levels of fatty acids in other materials (such as cocoa and shea butters), and use these ingredients to stabilize the emulsion. When used in a moisturizer, this forms a protective barrier on the surface of skin, greatly assisting moisture retention.
The surfactant qualities of glyceryl stearate and PEG-100 stearate allow oil and water to mix. The stabilizing effect of these two ingredients means that the product remains blended and will not separate. Creams and lotions are water and oil droplets held together by materials called emulsifiers: without them, oil droplets would float on top of the water.