The main goal for respiration is to chemically break down or oxidize the food, like sugar, into energy, which help us to complete daily energy needs such as growth, repair, movement etc.
In respiration, theres aerobic respiration and anaerobic respiration. They occur with oxygen supply and without, respectively. If we're not in vigorous exercise, our body should be doing aerobic respiration. It turns glucose and oxygen into carbon dioxide, water, and energy. Anaerobic respiration can be divided into muscles respiration and yeast, which both are really different.