What Are The Two Main Functions That The Human Ear Performs?

The ears two functions are hearing and balance control. We often take for granted the gift of hearing, and can't imagine what life would be like without the ability to communicate with others or to enjoy music and all the other sounds in our environment. However, in order to enable us to hear and interpret those sounds, there are an enormous number of tasks that the auditory system must perform, as we will see. It far surpasses any existing sound reproduction system around.
The  range of the auditory system, which is the interval between the softest and loudest sounds that the ear can hear, is more than 120 decibels.
The ear is sensitive enough that it can detect sounds which are so weak that the air molecules move less than the diameter of an atom! But yet it is also able to handle much louder sounds without overloading and saturating ("maxing out") which would cause undesirable distortion. This is accomplished by means of an automatic gain control system (AGC) which attenuates the response to louder sounds.
In terms of frequency, the human ear can hear sounds as low as 20 Hz all the way up to 20,000 Hz.
Bats use this precision to echolocate their prey. They actually have a fully functional sonar system which measures the elapsed time between an emitted stimulus and its returned echo to precisely locate a fast moving object and identify what it is, humans cannot do this  but can locate direction.
The outer ear consists of the organ on the side of our heads that we usually call simply "the ear". Also included in the outer ear is the ear canal. This is the hollow tube that leads from the pinna into the head. It terminates in the eardrum  The purpose of the external ear is to transmit sounds from the outside world into the more internal parts of the auditory system.
The ear canal also plays a role in shaping the spectrum of incoming sounds. It does this in a manner similar to an organ pipe where certain wavelengths tend to reflect back in such a manner so as to cause constructive interference which acts to strengthen the sound. Other frequencies reflect back in a way which causes destructive interference and are thereby weakened.
At the inner end of the ear canal is the eardrum which is a small membrane about 1 cm in diameter. Its purpose is to seal off the delicate organs of the inner parts of the auditory system so that foreign matter and bacteria don't enter which could otherwise clog the system. The fluid in the inner ear regulates our balance which is why we become dizzy while spinning.

To hear and also to have balance