what do you mean by the force of friction is observed whenever two surfaces are in relative motion ?????
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other.
And relative motion means when an object is in motion when it is continuously changing its position relative to a reference point and as observed by a person or detection device. For example, you can see that an automobile is moving with respect to the ground.
so the answer to your question is that friction is experienced when to bodies move with respect to each other.