The light is directly over the shoulder of the camera and her shadow is cast directly behind her.
The light is 45 degrees to the right of the camera and a shadow is cast on the right of her face. Notice how you can see the shadow of her nose going towards the same direction.
The light is 45 degrees to the left of the camera and her shadow is cast behind her to the left.
The light is 180 degrees to the subject's left. Half of her body is lit while the other half is dark.
The light is shining directly on the backdrop and the subject is completely dark.