Breathing is the physical process where you inhale and exhale air in and out of your lungs. Inhaling brings in air containing Oxygen, which is absorbed and exchanged for Carbon Dioxide. The Carbon Dioxide, now in the air inside your lungs, is expelled when you exhale. The Oxygen is carried in your blood to the cells around your body where respiration takes place. Respiration is a chemical reaction where Oxygen is used to breakdown Glucose in order to generate energy which is then used by the cell to function.