Voice-over (also known as off-camera or off-stage commentary) is a production technique where a voice that is not part of the narrative (non-diegetic) is used in a radio, television production, filmmaking, theatre, or other presentations. The voice-over may be spoken by someone who appears elsewhere in the production or by a specialist voice actor. it is pre-recorded and is placed over the top of a video. Commonly used in documentaries or news reports to explain information.(TKD)