Typically a V-shaped cutout that can prevent the achilles tendon from being irritated.
Heel Counter
Helps keep your foot stable and cups the heel.
Insole or Sockliner
A flexible plastic foam insert that helps with shock absorption and arch support.
Midsole
A thick layer of shock absorbing and supportive materials.
Toe Box
Part of the shoe's upper that encases your tees and forefoot.