Aerobic means "with oxygen," meaning oxygen - carried by your cardiovascular system to your muscles, as the fuel; anaerobic means "without oxygen." With training, aerobic fitness lets you swim or run or cycle for long periods. Anaerobic exercise is the type where you get out of breath in just a few moments, such as when lifting heavy weights to improve strength, when you sprint, or when you climb a long, steep flight of stairs. It’s something that’s used in bursts of intensity and depletes rapidly.
Anaerobic exercise uses glycogen, which is largely stored in muscle or the liver. Glycogen, (a glucose source) is converted to adenosine triphosphate, the active fuel. (The process of converting it to energy is glycolysis)
Strength-training performed in a few-reps, heavy-weights format uses primarily anaerobic resources. The same thing done with somewhat lighter weights and briefer rests will be more aerobic, using oxygen as main fuel. For strength, endurance and power, both aerobic and anaerobic capacity should be developed.