What type of light is used to illuminate a subject or object from behind?

The correct type of light used to illuminate a subject or object from behind is backlight. Backlighting is a technique often employed in photography, film, and stage productions to create depth and separation between the subject and the background. By lighting the subject from behind, the edges of the object are highlighted, which can enhance its shape and create a visually appealing silhouette. This technique can also add mood and dimension to the image, as it highlights the contours rather than the details of the subject.

While projection light can direct light in a specific pattern or onto a screen, it is not specifically defined by its placement relative to the subject. Background light generally refers to illumination applied to the background elements, rather than the subject itself. Stage light is a broad term that encompasses various types of lights used in performances, without the specific focus on backlighting. Thus, the definition and function of backlight are precisely what make it the correct answer in this context.