Various leathers are available; the type used in the manufacture our footwear depends on the use to which the footwear will be put:
Smooth leather: the upper layers of the hide, prone to scratching
Nubuk leather: upper hide layers, slightly ‘roughed up´ and thus relatively insensitive to abrasion, ideal for trekking boots
Velour leather/ split leather: middle hide layers, fibres visible, very durable, limited elasticity and tear-resistance.
Reversed leather ("hunting" or "roughout" leather): very tough and durable outer surface with stable reverse side, ideal for mountain boots.
In its naturally occurring form, cow hide is about 6-8 mm thick and thus must be split. The decision about where to make the split ( thick grained leather + thin split leather or vice versa) is made during the tanning process.