A reflector is used to redirect or 'bounce' light from another light source toward the subject. Reflectors can be made of various materials from foam core to nylon. The more reflective the surface, the more the reflector will provide strong directional light. Less smooth surfaces provide a more diffused, softer light.
Professional reflectors for photography come in many shapes and sizes. Many are manufactured with white, silver or gold colored material used to provide a color cast in order to cool or warm a photo. Portable refectors can be folded and stored for location shots or traveling. Reflectors can even be used as backgrounds in a pinch.