The cochlea is a spiral-shaped structure in the inner ear that plays a crucial role in hearing. It is filled with fluid and contains tiny hair cells that convert sound vibrations into electrical signals. These signals are then sent to the brain through the auditory nerve, allowing us to perceive sounds. When sound waves enter the ear, they travel through the ear canal and vibrate the eardrum. This vibration is transmitted to the cochlea, where the movement of fluid stimulates the hair cells. Different frequencies of sound activate different parts of the cochlea, helping us distinguish between various pitches and tones.