Three-point lighting is a very common lighting technique used in still photography. By using three separate light sources, the photographer can illuminate the shot's subject however desired, while also controlling the shading and shadows produced by direct lighting.
The key light, as the name suggests, shines directly upon the subject and serves as its main illuminator; more than anything else, the strength, color and angle of the key determines the shot's overall lighting design.
The fill light also shines on the subject, but from a side angle relative to the key. It balances the key by illuminating shaded surfaces, and lessening or eliminating chiaroscuro effects, such as the shadow cast by a person's nose upon the rest of the face.
The back light shines on the subject from behind, often (but not necessarily) to one side or the other.
Soft is the term for the light that surrounds and wraps that subject of the photograph. There are two main factors that you must take in consideration while taking pictures with a soft light, which are: distance and the size of light source.
Hard light sources cast shadows whose appearance of the shadow depends on the lighting instrument. The shadows produced will have 'harder' edges with less transition between illumination and shadow. The focused light will produce harder-edged shadows.
