With the Foilcraft Junior and the Foilcraft 4x3, it is now possible not only to emboss with foil but also deboss without foil. With embossing for example, if you are using mtallic gold foil, it will leave a metallic gold print onto your item whereas when you deboss without foil, it will leave a deeper impression into the leather without any foil colour.
With debossing, you would normally increase the temperature, apply extra pressure a little longer than you would do for embossing. On some leathers, the actions of debossing may actually change the shade of the leather, which adds to the charm and gives the leather that extra prestige look.