Three point lighting

key light: 

The key light is the first and usually most important light that a photographer, or other scene composer will use in a lighting setup. The purpose of the key light is to highlight the form and dimension of the subject.

1. most important light (main one)
2. dramatic light look
3. makes it more even
4. strongest as it gets closer 

fill light: 

A supplementary light used in photography or filming that does not change the character of the main light and is used chiefly to lighten shadows. 

1. light gets safer when you move it away
2. further away makes the light less intense, but also softer as you push it further away.

Hair light:

 A hair light is generally placed behind the model and about 3 feet above the head, with the hight angled down and slightly forward to strike the top of the head and shoulders.

1. makes it looks like a film
2. on its own it makes it look dramatic 
3. makes it looks dreamy 
4. makes it pop out at you when you have all three lights on