Voice-over 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 is read from a script and may be spoken by someone who appears elsewhere in the production or by a specialist voice actor. Synchronous dialogue, where the voice-over is narrating the action that is taking place at the same time, remains the most common technique in voice-overs. Asynchronous, however, is also used in cinema. It is usually prerecorded and placed over the top of a film or video and commonly used in documentaries or news reports to explain information.
A man recording a voice-over
Diegesis is a style of fiction storytelling which presents an interior view of a world in which the narrator presents the actions of the characters to the readers or audience.
In the game Dead Space, the colored spine of the player's spacesuit is used to indicate the health points of their character. This is rendered within the environment of the game, as part of the player's character. Ammo, mission updates, and several key menus are also rendered in the game world, which are viewed by the player's character.