Three point Lighting

Key light:

This is the main light. The purpose of the key light is to highlight the form and dimension of the subject.

Fill light:

This is a secondary light, an extra light used in photography or filming that does not change the character of the main light and is used especially to lighten shadows.

Back light:

Back light is the process of enlightening the subject from the back. This creates a glowing effect on the edges of the subject, while other areas are darker. The backlight can be a natural or artificial source of light. When artificial, the back light is usually placed directly behind the subject in a 4-point lighting set up.