The key differences between aerobic and anaerobic activities lie in their energy systems and intensity levels. Aerobic activities, like running and cycling, rely on oxygen for sustained energy over extended periods, promoting cardiovascular fitness. In contrast, anaerobic activities, such as weightlifting or sprinting, depend on energy sources stored in muscles and are performed at high intensities for short durations. Both types of exercise are essential for a balanced fitness routine, providing varying benefits to endurance and strength.