Silhouettes add to the mood of a photo. The more shadows and shapes captured, the more of a story there is. To make a silhouette possible, the background has to be whiter than the subject. The photographers point of view has to be in the perspective of a shadow. These kinds of photos can be dramatic. The shape of a subject will be shown more and will be represented more heavily. The outline matters so if the subject makes a wrong face or blinks it wont matter since the subject will be completely blacked out. The background must have no distractions so that the silhouette stands out more. It is possible to even underexpose so its important to get all things correct.