A hearing aid is a battery operated device that has a part inserted into your ears (like earbuds, in ear headphones) and a housing hooking over your ears (worn behind your ear).
How it works?
Pretty simple, it enhances the sound from the outside world so a person with hearing loss can live a normal life as they used to be.
A microphone will capture the sound (some hearing aids equipped with dual microphone), the sound signal is electrically sent to a circuitry and amplified. Eventually the output sound is delivered to wearers on the driver.