The ear is divided into three parts: the outer ear, the middle ear and the inner ear. The auditory nerve transmits information from the inner ear to the brain for processing.
The outer ear comprises the portion of the ear that can be seen known as the pinna, as well as the ear canal and the eardrum. The pinna collects sounds from the environment; sound waves travel down the earcanal and set the eardrum into vibration.
The middle ear is an air-filled cavity. Vibrations from the eardrum are transmitted through the ossicles (a chain of tiny bones in the middle ear) to the hearing organ. The ossicles are named the malleus, incus and stapes (also known as the hammer, anvil and stirrup due to their shapes). The Eustachian tube connects the middle ear to the back of the throat. The Eustachian tube's job is to equalize pressure between your ear and the atmosphere. When you drive up a hill you may feel your Eustachian tubes open to equalize pressure.
The inner ear is comprised of the balance organ and the hearing organ. The hearing organ, cochlea, is a snail shell shaped organ responsible for transforming the vibrations from the middle ear into a neural code that may be used by the auditory nerve. This neural code travels from the cochlea via the auditory nerve to the brain where we perceive sounds.