Nubuck leathers are in essence a fortuitous by-product of splitting a leather hide to the desired thickness. The underside layer created from this splitting process can then be buffed to create a napped suede.
Suedes and Nubucks are produced very similarly, the key difference being the side of the hide that is finished. Suedes have been buffed on the underside of the hide, whereas Nubucks have been buffed on the grain side.
A typical distant characteristic that can be used to tell suedes and nubucks apart, is their nap. Suedes tend to have slightly larger fibres on their top surface, nubucks have a much finer, velvety nap due to the shorter fibres on the grain side of the hide.