In computer graphics, light usually consists of multiple components. The overall effect of a light source on an object is determined by the combination of the object's interactions with these components. The three primary lighting components (and subsequent interaction types) are diffuse, ambient, and specular.
Shadows are created by testing whether a pixel is visible from the light source, by comparing the pixel to a Z-buffer or depth image of the light source's view, stored in the form of a texture. To get softer shadows, the shadow radius is increased.
Reflections depend on the way in which a material reflects incoming light rays. If a material is rough then it will scatter light rays and so won't produce clear reflections.