Glycolysis is common to both aerobic respiration and fermentation. Fermentation stops immediately after glycolysis (except for an additional step wherein the NADH formed is reverted to NAD+. Fermentation is inefficient in that it has a net yield of 2 ATP molecules per glucose molecule. Aerobic respiration carries on after glycolysis. The products of glycolysis (2 pyruvate molecules) are further oxidized in the Kreb cycle. Every time the molecules are oxidized, energy is released. This energy is temporarily stored in NADH, FADH2, and ATP. During chemiosmosis (which occurs in the electron transport chain), the NADH and FADH2 is converted (indirectly) to ATP. Because aerobic respiration oxidizes glucose more completely than fermentation, it is a much more efficient process. Depending on what kind of cell it occurs in, aerobic respiration can yield 36-38 ATP molecules per molecule of glucose. I hope that helps. Good luck!