The document discusses respiration in organisms. It explains that respiration includes both breathing and cellular respiration. Breathing involves intake of oxygen through lungs, while cellular respiration involves the oxidation of foods like glucose in mitochondria to release energy. There are two types of respiration - aerobic respiration, which uses oxygen to fully break down glucose, and anaerobic respiration used by microbes which breaks down glucose without oxygen. The document also provides details about human respiration and the respiratory system.