This is called the back light . Well think back to your Physics lessons and you might also be able to remember the inverse square law. This states that 'the intensity of light observed from a source of constant intrinsic luminosity falls of as the square of the distance from the object'. The camera goes 'Hey, loads of white I better set my exposure to that', so when you come to look at your footage all you can see it a silhouette of your subject and you can hardly see their face. Light not only differs in intensity, but also in its colour.
Lights have different colour temperatures.
Your eyes can sort this information out, but the camera tends to make everything look all one colour if its on the wrong setting. So remember to check the white balance on your camcorder. White balance is essentially what colour your camera thinks is white. Some cameras have buttons for this i.e. indoors, outdoors etc. Try changing your camera's white balance for effect.