The portion of the object that is not in light is in shadow. The value and color will be affected by reflected light on the shadow side of the object.
What is commonly called the cast shadow is actually the absence of light on another object.
Reflected light is light that bounces off other objects onto the shadow side of an object. The amount of reflected light is dependent on the intensity of the light source, the angle of reflection, and the surface quality of the reflecting object.
This old abandoned house is in shadow. The light is behind the house and just left of center. Looking at the roof, notice that one side is receiving light and the other side is in shadow. There is a slight cast shadow from the roof that is in shadow on the roof that is receiving light. Trace the line of that cast shadow backwards and it points to the light source.
The upper front of the building is receiving reflected light from the sky and is slightly bluer in color. The portion on that side under the porch roof is receiving reflected light from the ground which is grass and is lighter with the color of the grass.
The "cast shadow" on the grass is transparent. Cast shadows are never black as they appear in many photographs.
Remember, all objects will have a highlight, a light side, a shadow side, reflected light, and will also cast a shadow.