Understanding shoe lingo can help you sort through the many styles and brands of athletic shoes. Here are a few features that can affect fit and function. 1. Gel, foam or air midsole: These materials cushion and reduce impact when your foot strikes the ground. 2. Insole: This cushions and supports your foot and arch. 3. Upper: This holds the shoe on your foot. A mesh upper allows better ventilation than a leather or synthetic upper. 4. Toe box: This is the space for your toes. A roomy toe box helps prevent calluses.