A contact force is a force that acts between two objects only when they are touching. What is a Force

A force between objects in contact with each other. A contact force can be attractive (as in a tension force), repulsive (as in a normal force), resistive (as in friction), restoring (as in a spring force), or arbitrary (someone pushing and pulling on things).

In physics, a contact force is a force between two objects (or an object and a surface) that are in contact with each other. This is distinct from a non-contact force (a force that acts over a distance), such as gravity or magnetic attraction/repulsion.