The document is a submission about the respiratory system. It lists and describes the main parts of the respiratory system including the nostrils, nasal cavity, pharynx, trachea, bronchi, bronchioles, and alveoli. It explains that air enters through the nostrils and is transported through the nasal cavity, pharynx, and trachea before reaching the lungs and branching into smaller structures like bronchioles and alveoli, where gas exchange occurs.