Key Light- This is the brightest light and the main light source of our subject.
Fill Light- The shadows created by the key light are filled in by the fill light; the fill light is positioned on the other side of the camera from out key light and it illuminates the shadows cast by the key light. The fill light should be less bright than the key light so that there is still contrast on either side of the subject.

Backlight-the purpose of backlight is to create a rim of light around the subject in order to distinguish the subject from the background- positioned behind the subject either higher or lower.