Cowhides, in their natural state, are too thick to be used for most conventional purposes. They first must be split into thinner layers.
Full Grain Leather is outermost layer of the hide. It is leather that has not been corrected or modified outside of removing the hair. Full grain leather is often seen as the most authentic type of leather because it maintains all of the texture from the original cowhide.
When the hide is split into layers, Split Leather is taken from the inner layer of the hide. It is typically more delicate than full-grain leather, and is often used to create suede.
Top-Grain Leather is the same as full grain leather but the cowhide that is used is most often severely defective. To remedy this, top grain leather is typically sanded and then a finish coat is added to the surface. It is usually less expensive and has higher resistance to marks and blemishes than full-grain leather.