Standard setup:

1.   Key Lighting – The Key light is the primary light source in this style of setup.  It is pointed from the side of the object to create a dynamic effect of light.
2. Fill Light –  This light is used to create a nice balance of light so the shadows are minimal preventing a chiaroscuro effect, and creating slight “butterfly” shadows in and around the object’s face.  This makes the lighting more intimate in the environment and therefore quite personnel.
3. Finally, the back light is used to separate the object themselves from the background.  This strengthens, enhances and above all defines the objects features to appear 3 dimensional.

How do the three lights affect a photograph?