UAVs or Unmanned Aerial Vehicles are unpiloted aircraft. Their types of aircraft do not have a cockpit meaning they are specifically designed to fly without a pilot. Although, there is still a type of UAV that does need to be controlled, most especially during certain situations when critical decisions need to be made.
This actually led to the creation of RPVs or Remotely Piloted Vehicles. RPVs also share the same features with UAVs, just that the service of a pilot will still be needed for RPVs. In a simple term, RPVs are remotely piloted vehicles meaning the pilot will not always be on board but in a very safe location.
Another difference between UAVs and RPVs is the absence of a cockpit in the former and the presence of a cockpit in the latter. Since RPVs are basically just like the common piloted planes, they can be used to perform the functions of the piloted planes, whereas the roles of UAVs are limited in this respect.