A shadow is a dark area or shape produced by a body coming between rays of light and a surface. They are made when an object blocks light.
You need three things to make a shadow:
1. a form of light
2. something to block the light
3. a surface for the shadow to fall on
Shadows can change their size. As light moves towards the object, the shadow becomes larger. As light moves away from the object, the shadow becomes smaller.