What is an emulsion?
Very simply an emulsion is a mixture of water and oil.
What is an emulsifier?
Oil and water do not mix, if they are shaken together they will eventually separate out into 2 layers. An emulsifier stops this from happening. This allows you to create a stable mixture of oil and water.
How do emulsifiers work?
An emulsifier is a molecule with both hydrophilic and hydrophobic properties.
The hydrophilic head loves to be in water and the hydrophobic tail is happiest in oil. These properties allow small globules of oil to exist in water without joining together, separate layers of oil and water do not form.