According to the BBC, anaerobic respiration involves the incomplete breakdown of glucose and only releases about 5 percent of the energy released by aerobic respiration. It also produces lactic acid as a waste product rather than carbon dioxide and water.
As Heather Scoville at About.com explains, anaerobic respiration processes are primitive in comparison to aerobic respiration. The beginning of the process is very similar, but it either stops part-way through the pathway because the oxygen is not available for it to finish, or it joins with another molecule that is not oxygen as the final electron acceptor. The most commonly known anaerobic processes are known as fermentation and release byproducts of either lactic acid or alcohol in most cases.