To keep it simple, we yield high levels of ATP (energy) from our aerobic metabolism, specifically our Fat Oxidative and Aerobic Glycolytic systems. However these energy systems are slow to produce energy. When we need energy for high intensity efforts, we lean on our anaerobic systems (ATP-PCr and Anaerobic Glycolytic) to harness energy quickly. The yield of ATP is much less compared to the aerobic systems and we also create a large amount of metabolic waste which is why we prefer to stay aerobic to accomplish most tasks (and why we drew the 4Q Metabolic Model with larger Sub-Threshold quadrants).
Note: You will not be quizzed on the complexity of the energy systems.