FPV – First Person View.  Generally means piloting a model aircraft/UAV from a first person onboard perspective. This is accomplished via video camera and video transmitter that sends the video stream to a ground station receiver and video screen or goggles for viewing in real time by the pilot/operator. Some FPV setups also allow for camera movement, allowing the operator to look around by the use of a head tracking system or manual RC control of the camera.

A FPV Device as defined by Transport Canada:

means a device that generates and transmits a streaming video image to a ground station display or monitor giving the UAV pilot who is viewing this video, the illusion of actually flying the UAV from an onboard pilot perspective.

Wikipedia – First Person View