Chiaroscuro is the use of contrasted light and shadow. It was developed during the Renaissance in portraiture - artists used light to illuminate objects and faces, particularly one side of the face which gave a dramatic effect and added another dimension to the painting.
Photographers use this technique to highlight what they want to be seen. Strong tonal contrasts can be use to create dramatic effects in photographs and in films. It can also be used to hide a part of someone or someones identity; having the direction of light from behind so only a silhouette can be seen.
I used 1 point lighting to achieve an extreme version of chiaroscuro so only some of the face is illuminated. The contrast of shadow that takes over the rest of the photograph helps to exaggerate this.