Most soaps remove grease and dirt because some of their components are
surfactants (surface-active agents). Surfactants have a molecular structure
that acts as a link between water and the dirt particles. This loosens
the particles from the underlying fibers or surfaces to be cleaned. One
end of the molecule is hydrophilic (attracted to water), and the other
is hydrophobic (attracted to substances that are not water soluble). This
peculiar structure allows soap to adhere to substances that are otherwise
insoluble in water.