Counterbore is typically a specialized drill bit that creates the hole for the body of the fastener and the larger sized cavity for its head, both at the same time. Usually, the fastener is a flat-bottomed screw such as a round head or a pan head screw.

Pilot Hole allows the screw threads to cut directly into the hole, which reduces the risk of splitting wood near an end or edge.

Countersink is an angled taper applied to a hole that allows a fastener (usually a flat head screw or similar) to sit even with, or below the surface which has been countersunk.