Originally, the term ‘drone’ referred to types of unmanned aircraft (aeroplanes, helicopters, balloons, etcetera) pre-programmed with a flight plan. Nowadays the terms includes all types of unmanned machines, like robots, submarines and off-road vehicles.

The most common drone however, is the aerial (flying) one, with the distinction being made between Remotely Piloted Aircraft (RPA) and autonomous aircraft. An RPA is flown by a pilot located at a ground control station, while the autonomous aircraft flies without human intervention according to a flight plan, possibly using automation systems. Many newer drones can be operated both ways.