Put these words in order to show how oxygen gets into your blood: mouth, trachea, alveoli, bronchi.
The trachea is a tube which passes between the mouth and the lungs (this is also sometimes referred to as the windpipe). This is a separate tube entirely from the esophagus. The function of the trachea is to allow the passage of air while the esophagus allows the passage of food and drink from the mouth to the stomach.
When the trachea reaches the lungs, the passageway branches into several smaller tubes which also allow the passage of air. These smaller tubes are called the bronchi. (Note that the word bronchi is plural, bronchus is singular).
Alveoli are small sacs within the lungs where gas exchange between the air and the blood actually occurs. Alveoli are attached to the bronchi.
Thus, air passes from the mouth, to the trachea, to the bronchi,, and finally to the alveoli.