The edges of the subject would show surprising colour effects.
This effect usually hides details, causes a stronger contrast between light and dark, creates silhouettes and emphasizes lines and shapes.
The sun, or other light source, is often seen as either a bright spot or as a strong glare behind the subject.
[1] Fill light may be used to illuminate the side of the subject facing toward the camera.
The subject is generally considered silhouetted when there is a lighting ratio of 16:1 or more.