The ear is a very complex organ that we could divide into three parts:
The external ear formed by the bowl of your ear, the auditory canal and the eardrum. It is responsible for conducting sound to the inside of the ear.
The middle ear is a cavity filled with air that contains the three smallest bones in the human body: Hammer, anvil, and stirrup. These bears are on one side in contact with the eardrum and on the other communicate with the inner ear.
The cochlea and semicircular ducts form the inner ear. The cochlea is responsible for sound treatment, while the semicircular ducts are responsible for balance.
The cochlear duct, filled with fluid, has fine hair cells throughout. The movements of the middle ear bones are transmitted to the fluid and stimulate the hair cells which in turn activate the auditory nerves. Sound information is carried by nerves to the brain for processing and interpretation.