* Cellular Respiration: This is the process where glucose is broken down in the presence of oxygen to produce energy (ATP), carbon dioxide (CO2), and water (H2O).

* Fermentation: This is an anaerobic process (without oxygen) where glucose is broken down to produce a small amount of ATP and byproducts like lactic acid (in animals) or ethanol and carbon dioxide (in yeast).

Key Differences:

* Oxygen Requirement: Cellular respiration requires oxygen, while fermentation does not.

* ATP Production: Cellular respiration produces significantly more ATP than fermentation.

* Byproducts: The byproducts of cellular respiration are CO2 and water, while fermentation produces lactic acid or ethanol and CO2.

Therefore, ATP is a product of cellular respiration but not fermentation. While fermentation does produce a small amount of ATP, its primary purpose is to regenerate NAD+ so glycolysis can continue.