An emulsion is described as:

An emulsion is correctly described as a mixture of two or more immiscible substances aided by a binder. In the context of skincare and cosmetic formulations, emulsions typically involve a combination of oil and water, which do not naturally mix due to their differing polarities. The binder, often an emulsifying agent, helps to stabilize this mixture, allowing the two substances to coexist without separating.

This definition is particularly important in esthetics, where emulsions play a significant role in product formulations, such as creams and lotions. The proper incorporation of emulsifiers ensures that the final product retains a homogeneous texture and provides the desired effectiveness on the skin.

Other options do not accurately represent what an emulsion is. For instance, a mixture of two versatile solids does not involve the essential characteristic of immiscibility. A solution containing one type of liquid implies a homogeneous mixture rather than an emulsion, which involves two distinct phases. Lastly, a gas mixed with a liquid does not characterize an emulsion, as the concept of emulsions pertains specifically to the combination of liquids with different properties.