Okay, here is my understanding and I do not know how right or wrong I am. I have seen all of the different types of leather while shopping for furniture with my parents.
Naked leather - Virtually straight off the cow, all imperfections still exist. There is no buffing and sanding done to the skin and there is a grain. If you rub your hand across the leather or sit on it, the leather may scratch. Rare to find on furniture (mostly high end) and I have never seen it in a car. The leather is dyed to provide the desired color but there are no surface pigments or coatings. Because of this, the leather will absorb body oil, lotions, water, and anything else you spill on it. Due to not having a surface pigment (think of a paint), the color is not always consistent.
Next there is leather that is buffed and sanded, dyed, and has a clear surface coat applied. As a result of the sanding, buffing, and surface coat, fewer imperfections exist, the leather has a smooth surface, will not scratch, and will not absorb.
Most common type of leather is the one that is buffed, sanded, dyed, and then has a pigment applied to the surface. The thickness of the surface coating has a great impact on how soft the leather is. Leather that is very stiff or plastic like has a thick coating (also pretty common on less expensive cars). Thinner surface coating allows the leather to be more representative of naked leather in terms of softness and comfort.
Aniline - Leather that uses only a dye for coloring is called aniline leather. The surface is not "painted" with a matching pigment and as a result, it looks more natural (imperfections, more supple). Full aniline leather is the most expensive because only the highest of quality of hides can be used.
Pull-up Aniline - In addition to the dye, there is a coat of oil and/or wax on the surface to give a distressed look. It scratches easily and the scratched areas will be lighter in color.
Semi-aniline - These leathers use both a dye and a surface pigment. The dye is carried through the skin and as a result, less surface pigment is required to achieve even coloration (thinner surface coat). Semi-aniline leathers are more representative of aniline leather (naked leather) than pigmented.
Pigmented - Often embossed, this leather has a heavy surface coat of pigment. This is the most common type of leather for furniture and automobile use. It does not scratch as easily, gives a uniform color and appearance, and resists fading.
Nubuck - An aniline leather that is brushed to create a texture similar to velvet. Not to be confused with suede; suede is the flesh side of the leather and nubuck is the grain side. The brushing process actually breaks the surface making it very soft but at the same time, more absorbent than aniline leathers.
Finally, Coated Leather (also called Bycast) - It is produced by splitting the hide, melting a glue on the surface, and then rolling a film of colored polyurethane. Typically produced in only dark colors, it lightens when scratched. Very common for belts and handbags.
Whew. I'm done, I hope.
