3-point lighting is the standard format for lighting scenes in film, video, and photography. It is based around three light sources with differing roles to produce the best overall result. A dramatic affect can be created when using only 1 of the 3 lights to create a new atmosphere to the piece.
Key lights are the most significant lights in a 3 point setup. They are usually directed against one side of the subject and produce a large cast shadow on the opposite side.
Fill lights lower the intensity of the cast shadow made by the key light and is less intense than the other lights.
Back lights lift the subject away from the environment around them, and help to emphasize silhouettes as well.