A force exerted due to collision or pushing an object is known as pressure. A pressure on an object can be exerted by external factors or internal molecules.
For example, when atoms of a gas are colliding on the walls of a container then pressure is caused by them.
Stress is defined as the external force applied over per unit area of an object.
Gravity is defined as the force which tends to pull an object towards the center of the Earth.
Friction is defined as the force that resists the motion of an object when its surface comes in contact with the ground or it slides.
Thus, we can conclude that the effect of atoms colliding with the walls of a container is called pressure.
