Director , Sunderland International Airshow
The most simplistic view, it’s a flying windmill or even a rotating parachute, think of a sycamore seed gently floating down as it spins.
The rotor blades of the gyro are completely free wheeling in flight, being driven solely by the air going up through the rotor disk. There is no mechanical drive to the rotors in flight, the phenomenon of autorotation drives them, once airborne the rotors just look after themselves and keep spinning, even if the airspeed indicator is showing Zero!!