Dry Friction:
Dry friction (also called as coulomb friction manifests when the contact surfaces are dry and there is tendency for the relative motion.
Dry friction is further subdivided into two parts:
Sliding Friction
Fiction between the two surfaces when one surface slides over the other.
Rolling Friction
Friction in between the surfaces that are separated by balls or rollers. It can be pointed out that the rolling friction is always less than the sliding friction.