This is natural light coming straight from the sunset outside the window. My friend was staring out side the window, and the way the light hit her face in some places and did not hit her face in other places made the picture look really interesting.
This is artificial light. I took this picture with just the flash on my camera. This makes my cousins face look much paler, but also makes his eyes stand out much more.
The natural light makes a white brightness, more yellow-ish and with artificial light the picture has more of white, pale glow to it.