Compound is a word that is used to describe a combination of two or more things. In photography, a compound is a combination of two or more things that are used to create a single image.
The most common compound in photography is a combination of a lens and a camera. This combination is used to capture the light that is bouncing off of the subject and turn it into an image.
Other compounds that are used in photography include flashlights, reflectors, and filters. Flashlights are used to add light to a scene, reflectors are used to bounce light into the camera, and filters are used to change the color of the light that is being captured.