3 Point Lighting
Three point lighting is the standard method used in the visual media's. These include video, film, still photography and computer generated imagery.
By using three different positions, the subject can be illuminated however strongly the photographer wants, whilst also being able to control the shading and shadows produced by direct lighting.
Key Light
The key light shines directly upon the subject and serves as the principle illuminator. The shot's colour, strength and angle/placement of the key determines the shot's overall lighting design. In indoor shots the key is usually a specialised lamp, or a camera flash. During out door shoots, it is commonly the sun that takes the role of key light. However in this situation the photographer cannot control the position of the light, instead having to rearrange the set to best capture the light.
Fill Light
The fill light, like the key light, shines on the subject, but from a side angle relative to the key and is often placed at a lower position than it. The level of the subject's face is usually preferred.
It balances the key by illuminating shaded surfaces, and lessening or eliminating chiaroscuro effects, such as the shadow cast by a person's nose upon the rest of the face. It is usually softer and less bright than the key light (up to half), and more to a flood. Not using a fill at all can result in stark contrasts (due to shadows) across the subject's surface, depending upon the key light's harshness. Sometimes, as in low-key lighting, this is a deliberate effect, but shots intended to look more natural and less stylistic require a fill. In some situations a photographer can use a reflector (such as a piece of white cardstock mounted off-camera, or even a white-painted wall) as a fill light instead of an actual lamp. Reflecting and redirecting the key light's rays back upon the subject from a different angle can cause a softer, subtler effect than using another lamp.The Back Light
The back light (a.k.a. the rim, hair, or shoulder light) shines on the subject from behind, often (but not necessarily) to one side or the other. It gives the subject a rim of light, serving to separate the subject from the background and highlighting contours.Back light or rim light is different from a kick in that a kick (or kicker) contributes to a portion of the shading on the visible surface of the subject, while a rim light only creates a thin outline around the subject without necessarily hitting the front (visible) surface of the subject at all.