Lighting
What it does
Lighting can do a lot such as set the mood in a shot, change the appearance of a person or improve the quality of a shot.
if you have one light, it becomes our key light. Two lights usually go opposite each other.
Three lights could mean including a backlight. This helps define a person.
The Right Place for Your Lights
Key light. This is a light usually placed 45 degrees left or right of the subject. It helps see the person and should be the brightest light.
Fill light. This light is placed 45 degrees to the left or right of the subject, opposite to the key light. It should be dimmer than the key light and it helps fill in the shadows on the subject. In the example above It is filling in the subjects face.
Back light. This should be placed behind and above the subject. This gives the hair/head and shoulders of them an outline, seperating them from the background.