The bottom of a shoe, the part that is intended to come in repeated contact with the ground, is called the sole. Soles have been made from plant fibers, leather, wood, rubber, synthetics, plastic, and various combinations of these materials. Soles can be simple, a single material in a single layer, or they can be complex with multiple structures or layers and materials.
The insole is the interior bottom of a shoe, which sits directly beneath the foot under the footbed (also known as sock liner). The purpose of insole is to attach to the lasting margin of the upper, which is wrapped around the last during the closing of the shoe during the lasting operation. Insoles are usually made of cellulosic paper board or synthetic non woven insole board. Many shoes have removable and replaceable footbeds. Extra cushioning is often added for comfort (to control the shape, moisture, or smell of the shoe) or health reasons (to help deal with defects in the natural shape of the foot or positioning of the foot during standing or walking). This is a significant element of a pair of shoes; it must be able to absorb foot sweat. In addition, footbeds should typically use foam cushioning sheets like latex and EVA, which provide good wearing comfort of the shoe.
The outsole is the layer in direct contact with the ground. Dress shoes often have leather or resin rubber outsoles; casual or work-oriented shoes have outsoles made of natural rubber or a synthetic material like Polyurethane. The outsole may comprise a single piece, or may be an assembly of separate pieces of different materials. Often the heel of the sole has a rubber plate for durability and traction, while the front is leather for style. Specialized shoes will often have modifications on this design: athletic or so called cleated shoes like soccer, rugby, baseball and golf shoes have spikes embedded in the outsole to grip the ground.
The layer in between the outsole and the insole that is typically there for shock absorption. Some types of shoes, like running shoes, have another material for shock absorption, usually beneath the heel of the foot, where one puts the most pressure down. Different companies use different materials for the midsoles of their shoes. Some shoes may not have a midsole at all.
The bottom rear part of a shoe is the heel. Its function is to support the heel of the foot. They are often made of the same material as the sole of the shoe. This part can be high for fashion or to make the person look taller, or flat for a more practical and comfortable use.
Every shoe has an upper part that helps hold the shoe onto the foot. In the simplest cases, such as sandals or flip-flops, this may be nothing more than a few straps for holding the sole in place. Closed footwear, such as boots, trainers and most men’s shoes, will have a more complex upper. This part is often decorated or is made in a certain style to look attractive.
Lateral and medial
The outside part of the shoe is referred to as the lateral and the inside facing part of the shoe is the medial. This can be in reference to either the outsole or the vamp.