A certain amount of lighting can create a specific feel to the image. What I like about this photograph is that the background lighting matches perfectly to the model expression. In another words if the background color is bright, the mood will often be happy, excited, surprise, etc. The way the lighting is set up, the main light is placed in a 45 degree angle (I believe) and the filler light is placed under the model face/upper body. Overall, the expression on the model face matches perfectly to the lighting.
