What is an emulsifier（ chemical ）?

Emulsifiers contain both a water-loving head group and an oil-loving tail. When added to an o/w emulsion, the emulsifier surrounds the oil droplet with it’s oil-loving tail extending into the oil, and it’s water-loving head facing the water. (In a w/o emulsion, the emulsifier’s orientation is reversed.) In this way, emulsifiers lower the interfacial tension between the oil and water phases, and form a protective layer around the oil phase keeping the oil droplets evenly dispersed and preventing them from flocculating.

Cetyl alcohol and beeswax are not emulsifiers!