An unmanned aerial vehicle , commonly known as a drone and also referred by several other names, is an aircraft without a human pilot aboard. The flight of UAVs may be controlled either autonomously by onboard computers or by the remote control of a pilot on the ground or in another vehicle. ICAO classify unmanned aircraft into two types under Circular 328 AN/190:
The typical launch and recovery method function of an automatic system or an external operator on the ground. Historically, UAVs were simple remotely piloted aircraft, but autonomous control is increasingly being employed..
Unmanned aerial vehicles have mostly found military and special operation applications, but also are increasingly finding uses in civil applications, such as policing, surveillance and firefighting, and nonmilitary security work, such as inspection of power or pipelines. UAVs are often preferred for missions that are too dull, dirty or dangerous for manned aircraft. (source : wikipedia)