Anaerobic respiration takes place in the fluid portion of the cytoplasm of cells, away from the mitochondria or any other organelles. It begins with glycolysis, which breaks apart glucose and generates energy and a compound known as pyruvate, and also includes fermentation, which breaks down the pyruvate for more energy.
Fermentation in animal cells produces lactate as a waste product. It only occurs when the oxygen reaching cells is insufficient for their energy needs. In many other organisms, fermentation produces ethanol as a waste product. In both cases, these waste products still contain a great deal of energy that the cell cannot use, so these processes are less efficient than aerobic respiration.