Question

How do contact forces such as friction differ from gravitational and magnetic forces?

Answer 1

"Contact" means "touching".  A contact force can't act on an object unless
they're touching. Friction is a contact force.

Gravitational forces pull masses together even if they're not touching.
Magnetic forces pull a piece of iron toward a magnet even if they're not touching.

Gravitational and magnetic forces are "non-contact" forces.