The two branches of the trachea are known as brochi. Each bronchus that branches off of the trachea goes into one lung to deliver air to the lungs. There is one bronchus per lung.
The trachea is colloquially known as the windpipe because it is the anatomical structure that allows air to flow in and out of the lungs. It is a small tube that is less an inch in diameter and approximately four inches long. The trachea begins underneath the larynx and runs behind the sternum until it reaches the lungs. Here it branches into two bronchi which then enter the lungs and branch into more bronchi and eventually terminate into alveoli.