Drone vs UAV?

A drone is an unmanned aircraft or ship that is guided remotely or autonomously whereas UAV stands for Unmanned Aerial Vehicle, something that can fly without a pilot onboard.

An unmanned combat aerial vehicle (UCAV), also known as a combat drone, colloquially shortened as drone or battlefield UAV, is an unmanned aerial vehicle (UAV) that is used for intelligence, surveillance, target acquisition, and reconnaissance and carries aircraft ordnance such as missiles, ATGMs, and/or bombs in hardpoints for drone strikes. These drones are usually under real-time human control, with varying levels of autonomy. Unlike unmanned surveillance and reconnaissance aerial vehicles, UCAVs are used for both drone strikes and battlefield intelligence.

Aircraft of this type have no onboard human pilot. As the operator runs the vehicle from a remote terminal, equipment necessary for a human pilot is not needed, resulting in a lower weight and a smaller size than a manned aircraft. Many countries have operational domestic UCAVs and many more have imported armed drones or have development programs underway.