The Three Point Lighting Technique is a standard method used in visual media such as video, film, still photography and computer-generated images.
The three different lights are as follows:
Key light: This light is basically the main light and is usually the strongest and has the most influence on the look of the scene. It is placed to one side of the subject so that side is well lit and the other side has some shadow.
Fill light: This light is placed on the opposite side of the key light. It is used to fill the shadows created by the key. The light will usually be softer and less bright than the key light. To get this effect, you could move the light further away.
Back light: The back light is placed behind the subject and lights the back of the subject. Rather than providing direct lighting like the key light and fill light, its purpose is to provide definition and subtle highlights around the subject’s outlines. This helps separate the subject from the background and provide a three-dimensional look.