They are used in a variety of applications such as emulsifiers, wetting agents, detergents, blowing agents, and dispersants. The term "surfactant" refers to a mixture of surface-active substances and was coined around 1950. Surfactants have a hydrophobic (water-hating) tail and a hydrophilic (water-loving) head. The terminal end of most surfactants consists of a branched, straight, or aromatic hydrocarbon chain.

The head of a surfactant may have a net positive or negative charge, or it may contain two oppositely charged groups. Surfactants are classified as nonionic, anionic, cationic, amphoteric, etc. depending on their head composition. Common surfactants of each type include sulfates, sulfonates, phosphates, and carboxylates.