Surfactant is a contraction of surface active agent, a name given to describe the way these products work. Surfactants like shower gel work by removing grease and dirt because the molecules in the surfactant have a two-part structure, with a head and a tail. The head is hydrophilic (water-loving and dissolves in water) but the tail is hydrophobic (water hating but soluble in oil). Surfactants are good at cleaning because the tail is attracted into the oil, grease and dirt whilst the head stays in the water. As surfactant molecules surround the oil/dirt, the oil drop or dirt is pulled away from the skin/surface to make an emulsion in the water. The surfactant molecule is less reactive than the soap molecule and does not form the precipitate/scum that soaps form when they bond with metal ions in hard water.
Click on the diagrams to see what happens.