Your everyday muscles movements are made possible by the energy provided from Aerobic Respiration. However, during vigorous exercise your muscle cells may become short of oxygen.
Despite the increased heart and breathing rates, your bloody can simply not supply enough oxygen fast enough. When this happens, muscles obtain energy from Glucose.
But they have to do it without oxygen - This is called Anaerobic Respiration.
Negative of this is that lactic acid builds up in the muscles, which gets painful. This causes muscle fatigue and eventually they dont contract as efficiently.
Anaerobic does not release as much energy as aerobic
Advantage is that you can use yor muscles for a while longer