Great question! The human ear is a very delicate and complicated system — it goes much deeper than the bit you can see on the outside of your head. So: sound is vibrations in the air. These vibrations travel down our ear canal (the tube which connects the outside world to our ear drum). The ear drum then vibrates, and this passes the vibrations to 3 tiny bones (the smallest in the body!). These bones then pass the vibrations into a chamber full of fluid, which is curled up like a snail. There are some tiny, delicate hairs in the fluid, and the vibrations make these hairs shake. And when the hairs shake, that sends an electrical signal to the brain, which is interpreted as sound. I think it’s an amazing system 🙂 But it’s very delicate, and if a part of the system gets damaged then we almost always can’t repair it. So take care of your hearing!