Aerobic capacity is the maximum amount of oxygen the body can use in an exercise session.
Aerobic exercise (uses oxygen) is physical activity which increases your heart rate and breathing for a sustained period of time.
Exercise at a short, high intensity that does not utilise oxygen as energy but relies on the glycogen stored in muscles. This results in lactic acid build up.
Anaerobic threshold is the point in which your muscles start working without oxygen being present.
Atrophy is the wasting away of your muscle mass.