Shoes come in many different styles and fashion trends come and go with the seasons. Regardless of the style or how high- or low-fashion a certain piece of footwear may be, all modern shoes are generally constructed along a similar blueprint.
Shoe and Boot Distinction
A distinction must be made between boots and shoes in order to articulate the true meaning of an "upper" so that it is understood in all circumstances. On a traditional dress, casual or athletic shoe, there is not a shaft that follows the shape of the leg. If a shaft does exist then the footwear item is a boot and follows different definitions of "upper" and "lower" that used for traditional footwear.
Non-boot-shaped shoes are made of two main parts: the bottom of the shoe, or the "lower," that is under your foot and the "upper," or the part that wraps around the top of your foot. A shoe with a leather upper means that the exposed part of the shoe that is designed with aesthetic appeal in mind is made out of leather. Leather breathes better than vinyl, but is more costly. Some high-end shoes may be made out of exotic hides which cost even more than a shoe with a genuine leather upper. Athletic shoes may blend in synthetic materials like mesh to reduce weight and increase breathability.
The shape of a boot inherently contributes to a different definition of the term "upper." On a boot, particularly those of the cowboy variety, the part that wraps around the foot, the vamp, is referred to as the boot's "lower." The shaft part that follows the shape of the leg is the boot's "upper." The bottom of a cowboy boot is referred to in formal terms as the sole and heel.
Leather Upper Pros and Cons
Some high-end boots from companies such as Lucchese are crafted from exotic materials like alligator or ostrich. Boots with an exotic-hide upper and lower tend to be more expensive due to the extensive use of the hide. These full-on exotic boots are a sign of wealth and eccentricity, but few will see the upper portion. Boots that use an exotic hide on the lower, but a leather upper tend to cost less, but offer practical advantages beyond cost. The leather shaft tends to hold its shape better over time and is more resistant to the friction-wear that jeans can cause over time.