What is the difference between aerobic and anaerobic respiration?

The key difference is that aerobic respiration requires oxygen whereas anaerobic does not. Aerobic respiration is happening constantly in the body to release energy for processes such as protein synthesis whereas anaerobic respiration takes place during exercise, where there is insufficient energy. Aerobic respiration releases much more energy as the glucose is completely broken down, the glucose combined with oxygen forms carbon dioxide and water releasing energy. During anaerobic respiration less energy is released as carbon dioxide is only partially broken down, the glucose becomes lactic acid releasing energy. The lactic acid is what you feel as cramp during exercise.