Every object on earth experiences a force, called gravitational Force. Therefore, the gravitational attraction of Earth is an important force that pulls everything toward downwards on the Earth. When an object of mass m is placed on a table, the Earth pulls the body with a force mg towards downwards direction. Now, when this force is exerted by the body on the table, the table in turn exerts equal and opposite reaction force (−mg) on the body in the upwards direction which balances the weight of the body. This force exerted by the table towards upwards direction acts as reaction force.