Normal force is that what acts perpendicular to any surface.Its an action-reaction force pair perpendicular to body weight mg.
It is denoted as Fn
is the element, perpendicular to the surface of
contact, of the contact force used by, for instance, the surface of a
floor or wall, on an entity, preventing the entity from incoming the
floor or wall. In a static state it is sufficient to poise the forces
acting on the entity, like the force with which the entity pushes beside
the surface and friction.