Body Diode of a MOSFET
The body diode is part of the MOSFET structure and is always there. Sometimes a Schottky diode is added (co-packaged) because the body diode is slow recovery. Since the Schottky diode has a lower Vf it conducts most of the current.

It should be noted that the diode only comes into play in a configuration such as a half-bridge or H-bridge where the diode conducts when a different switch turns off. The internal diode is in the wrong place for a single switch controlling an inductive load- when the switch turns off the voltage across the switch rises rather than reversing.