Lighting choices can vastly change the appearance and tone of a photograph. A scene that seems cheerful and pretty when brightly lit can turn ominous and brooding if the lighting is made darker. Lighting also impacts the human face in a number of ways. Different kinds of lighting cast different shadows on the face, sometimes making the person look totally different. This highlights why people consider some photos of themselves to be flattering while other very similar photos are considered unflattering. Some photographers have been exploring just how different lighting can make a face look, as in the photo series and video linked below.
The same girl illuminated in soft lighting appears much younger than the photo taken in hard lighting.
The lighting also shifts audience perspective. A viewer may view the photo with hard lighting to be more sinister.
A video on the same subject: https://www.youtube.com/watch?v=6sgpeoWpO9w