Quite simply put - we need reflectors because they provide a reflective light to our images that lights just can't provide. They are able to be used at that 'other' light you hear photographers always talking about.
Controlling the sun in a back lit portrait is the focus of this lesson. There are several ways to solve this lighting dilemma; the most common and easiest is the flash fill setting on your camera. Most modern digital cameras have a auto "flash fill" setting that gives adequate results when you apply them to a back lit outdoor portrait.