Here's a breakdown:

* Cellular respiration is the process by which cells break down glucose (a sugar) in the presence of oxygen to release energy. This energy is used for various cellular functions.

* Carbon dioxide (CO2) is a byproduct of this process.

* Water (H2O) is also produced as a byproduct, along with energy in the form of ATP.

Let me know if you'd like more detail on cellular respiration!