1. Key Light
Key Light is the main or strongest light source. Key light lighting is directed from the damping side in front of the object to be taken.
2. Fill Light
Fill Light is a secondary light source or fill light on the opposite side of the key light. So, if the key light comes from the left, then the fill light comes from the right. Usually, the light intensity of the fill light should be lower than that of the key light. Fill light helps reduce shadows produced by the key light so that the image looks more natural.
3. Backlight
Back light is placed behind the subject and is used to light the subject from behind. The back light may be brighter or dimmer than the key light, the function of the back light is to add depth to the image, thus making the image appear three-dimensional.
A hair light is simply a lamp used to do exactly what it sounds like: light up the hair. Hair lights are generally placed behind the model and about 3 feet above the head, with the lights angled down and slightly forward to illuminate the top of the head and shoulders.