In three-point lighting system, three different kind of light sources are used to illuminate the subject in a scene. These three lights are:

• Key Light - The key light is the brightest light used in the scene. The key light is pointed to the front of the subject, a little from the side to give the subject the right kind of depth and exposure.
• Fill Light - The fill light is used to soften the shadows created by the Key Light. For example if the Key light is pointing from the left of the subject, the fill-light will be pointing from the right. The fill light seeks to reduce the shadows created from the brighter main light, and gives a much more uniform illumination to the side. By varying the intensity of Key Light and Fill Light a high-key video (where shadows are minimal) or low-key video (where shadows are much higher) can be generated. The choice depends on what kind of video is to be shot.
• Back Light - The back light is used to create the separation between the subject and the background, so that the subject stands out from the subject.

Essentially three-point lighting system is a guide to how lighting for a video can be setup. Each of the Key light, Fill light and Back light can be varied in intensity and position to deliver different kind of moods to the video.