Lighting is the manipulation of light to selectively highlight specific elements in each scene so they appear in a particular way. Light generates much of the mood of a film and can be used to indicate the time of day or night, the seasons, the state of mind of the character or to enhance a theme.
When discussing lighting, there are four key elements:
Naturalistic: Lighting that makes the scene look normal
Expressive: Using analogy for effect
Low Key: Dark lighting - shadows used for effect
High Key: Bright - lack of shadows
Lighting direction can also add meaning to the scene. Although most scenes are shot using three point lighting often other setups are used.
Side lighting casts hard shadows onto the surrounding setting. This can make a character seem imposing or a setting suspenseful.
Back lighting can give the character a sense of mystery or an almost holy appearance.