Basically, emulsifiers are a class of surfactants but the two terms (or even three terms: emulsifiers, detergents, and surfactants) are often used interchangeably. But generally, surfactants are used in cleansing products whereas emulsifiers in creams and lotions. But both ingredients can mix water with oils and thus making an emulsion. So, theoretically you could make a cream using a surfactant and on the other hand you could make a shampoo using an emulsifier. But even though the molecules of emulsifiers and surfactants are structurally similar, they do have their own characteristics and properties.