Good morning, Dae1678. Our muscle cells in our body have to use lactic acid fermentation whenever there isn't enough oxygen to support them. It goes through our bloodstreams to our livers to convert back to pyruvate then processed normally. Lactic fermentation is helpful for sprinters who run because of the short distance and ATP (energy) given. Although many people say that lactic acid fermentation causes soreness after exercising, this may not be the case after recent research. An example of lactic fermentation would be dark meat on a chicken bone because it does not have oxygen to turn a whiter color. As for aerobic respiration, it is how our body produces energy whenever given oxygen. The first step of aerobic respiration is glycolysis, second is the citric acid cycle, then the electron transport chain. Aerobic respiration is whenever you can run long distances, swim, and walk. An example of aerobic respiration would be lifting weights because you are needing the oxygen and energy given by the aerobic respiration to use your muscles. I hope I helped. If you have any more questions then do not hesitate to message me and I will gladly try to answer them. Have a great day.