The difference between aerobic and anaerobic endurance is how to get energy for the effort.
We use the oxygen to burn the glucose in aerobic endurance. This allows us to get more energy from the same amount of glucose but in a slower-way.
This route is used in long-term but low intensity activities such as walking, cycling or running at a moderate pace.
When we make a high intensity effort, our body does not have not enough time to use oxygen so we produce less energy with the same amount of glucose but faster than if we can use oxygen. At the end of this route of energy our body produces lactic acid. It is toxic and if this product is acummulated it doesn ́t allowed us to get more energy. This product is eliminated using oxygen but for this we have to lower the intensity. It is the way to get energy in the anaerobic endurance, for example in 400m running or in a sprint in cycling.