An example of this is the production of ammonia, know as the Haber Process. Since the reaction is very slow on its own, chemists add a catalyst to speed it up. Heterogeneous -the catalyst enters and exists in different phases of the reaction. The catalyst usually provided the area where gaseous molecules can adsorb on its surface, then it forms the product. The term adsorption is usually related with heterogeneous catalysts.
Adsorption is the collection of a substance on the surface of another.