Patent leather is a nice and super-glossy material, a thin leather that is lacquered with a surface of plastic. It is perfect to use on the outside panel of boots, toe part, tops and buckles. However, you should avoid having patent leathers on the entire foot part, as it can crack in the long run because it is not elastic and does not really shape itself to the foot in the same way as a regular leather does.
The thickness of the glossy leathers can vary a little but is usually between 18-22 mm.