The main difference between aerobic and anaerobic exercise lies in how energy is produced. Aerobic exercise requires oxygen and is sustained over longer periods, using fat and carbohydrates for fuel; examples include running, swimming, and cycling. In contrast, anaerobic exercise involves short bursts of high-intensity activity, relying primarily on glycogen stored in muscles; examples include weightlifting and sprinting. Both types are crucial for a well-rounded fitness program, as they target different energy systems and offer unique benefits to cardiovascular health and muscle strength.