We've all had it happen, we photograph a beautiful scene but when we view the image the sky is a blob of white and there are giant patches of black where we saw mild shadows on the ground. What is happening is that your camera can not record the full dynamic range of the scene. Dynamic range is the difference between the brightest point and the darkest point in a scene. The human eye can see over 20 f-stop equivalents in a scene because the eye constantly adjusts. While we think of a scene as one solid image, our eyes are constantly moving over different parts of the scene and adjusting accordingly. A camera works differently. It has one setting for the entire scene. As a result, the camera can only record around 8 f-stops in any one scene. This difference causes problems for many photographers and they are surprise at the overexposed highlights and underexposed shadows in a scene.
In the image above, yellow shows areas that are drastically underexposed and red shows the blown out, or drastically overexposed, highlights. To combat this type of situation you must either record a scene where there are not drastic lighting differences, or change the lighting. Fill flash, diffusers, and reflectors can all be used to add and subtract light as needed to even out the dynamic range of the image for photography.