There is a difference, lets start with stamped decorative concrete, stamped decorative concrete is poured as a slab, like any white concrete. After the surface has set, it will be stamped by the contractor with special stamps that have the desired pattern molded into to them. The surface then is colored as desired by the customer. Sometimes the entire pour will be colored. Decorative concrete overlay is spread as a thin layer over concrete or other compatible surfaces and is then stamped or smoothed and colored or stained to give the customer the desired effect.