Absorb refers to – take in. Such as – dray table salt absorbs water on a wet day. Carbon dioxide gas is absorbed by water as in soda water. Sound is absorbed by a soft surface. Heat and light are absorbed by a dark surface.
Absorption refers to – being absorbed and act of absorbing. When light passes through certain substances like a solution or gas, some of colours which make up the light are absorbed so that there are dark lines or bands in the spectrum. These dark lines are called absorption bands or absorption lines.
Reference: An Elementary Scientific and Technical Dictionary
What is Absorb?, What is Absorption?