If the adsorption is due to the weak van der waals forces between adsorbent and adsorbate, it is termed as 

Concept:

Adsorption is defined as the deposition of molecular species onto the surface.
The molecular species that gets adsorbed on the surface is known as Adsorbent and the surface on which adsorption occurs is known as Adsorbate.

Types of Adsorption

On the basis of interaction forces between adsorbate and adsorbent, adsorption is of two types. 

Physical adsorption:

This type of adsorption is also known as physisorption. It is due to weak Van der Waals forces between adsorbate and adsorbent. 

For example, H2 and N2 gases adsorb on coconut charcoal.

Chemical adsorption:

This type of adsorption is also known as chemisorption. It is due to strong chemical forces of bonding type between adsorbate and adsorbent.

We can take the example involving the formation of iron nitride on the surface when iron is heated in N2 gas at 623 K. 

Additional Information

Adsorption of gas on a solid is a spontaneous exothermic reaction.

Amount of heat liberated when a unit mass of a gas is adsorbed on the surface is called heat of adsorption.

The process of removal of adsorbent from the surface of adsorbate is known as Desorption.