In a professional setup, what is the name of the light that goes behind your subject to separate them from the background and make them stand out?

The light positioned behind your subject to separate them from the background and make them stand out is primarily known as a rim light. A rim light is placed behind and often to the side of the subject, directed towards them, to create a bright outline or highlight along their edges. This outline visually separates the subject from the background, adding depth and dimension to the image. The light achieves this by illuminating the subject's contours from behind, which increases the contrast between the subject's form and the background, making the subject appear more prominent and three-dimensional. Specific types of rim lights are named based on their placement and the effect they produce. A hair light is a rim light typically positioned above and behind the subject, angled to specifically illuminate their hair and shoulders. Its purpose is to add definition and a luminous quality to the hair, enhancing the subject's overall separation. A kicker light is another variation of a rim light, usually placed lower and more to the side of the subject. It projects light across the side of the subject, creating a more dramatic and focused edge highlight that emphasizes the subject's profile and contours, further enhancing their separation from the background.