What is a soft soap ?

Explanation

Chemical substances which concentrates at the surface of the solution or interfaces, from surface films, reduces surface tension of the solution and help in removing dirt and dust by emulsifying grease are called surfactants (i.e., soap and detergents).
Soaps are sodium or potassium salts of long chain fatty acids such as palmitic acid `(C_(15)H_(31)COOH)`. stearic acid `(C_(17)H_(3)COOH)` and lionic acid `(C_(17)H_(31)COOH)`
Potassium salt of fatty acids such as palmitic acid, staric acid and oleic acid are called soft soap.

Generally, potassium soap are soft to the sking so, they are named as soft soap.