Polysorbate 20 (common commercial brand names include Scattics, Alkest TW 20 and Tween 20) is a polysorbate-type nonionic surfactant formed by the ethoxylation of sorbitan before the addition of lauric acid.
Polysorbate 20 is commonly used to emulsify oils and water at a 1:1 ratio. It is a nonionic surfactant that is water-soluble and used as a dispersing agent. It is gentle and nonirritating. Normally, you need a solubilizer, such as Polysorbate 20, to mix your essential or fragrance oils into body sprays without separating. Combine equal amounts of your fragrance or essential oil and the Polysorbate 20 until you achieve a clear solution, then, add this mixture to your water or alcohol.
Source: Wikipedia, BrambleBerry