|3dRender.com : Glossary : Off-Screen Space|
Off-Screen Space - Space that is imagined, but not seen, by the audience. Off-screen space includes the areas that are behind the camera, above the top of the frame, below the bottom of the frame, or off to the sides. Sounds, lights, and shadows are often motivated by off-screen sources.
The Fourth Wall - The side of a set or shooting location from which cameras and lights are operated, which is not shown to the audience, or, in a theater, the side of a stage that is open towards the audience.
Wild Wall - A wall of a set that is designed to break away or be detached or removed in order to film through the wall.
Source: Digital Lighting & Rendering by Jeremy Birn, definition and 3D images adapted from the book by permission. This page © 2002 by Jeremy Birn.