What is the role of surfactant in laundry detergent

The main components of laundry detergent are surfactants (non-ionic + negative/cationic surfactants). The main component of laundry detergent is an anionic surfactant: sodium alkyl benzene sulfonate.

Surfactant molecules have both hydrophilic groups and oil-philic groups, which are also called "amphiphilic".

Because of this hydrophilic and liphilic property of surfactants, at the right concentration, they can form micelle in water: the hydrophilic head is attracted outward by the water, and the oil-philic tail is repelled inward by the water. So we can pull the oil stains off the clothes, so we can wash our clothes.