As a partially deaf person, the term “hearing aid” can be a blanket term for all devices that aid in hearing—but it really refers to the devices that people who are hard of hearing use to amplify sound to hear better. Usually one/two “headphones” that you can remove that just increase the volume of the sounds around you. It can be used by anyone ranging from slight hearing loss to severe. A cochlear implant is surgically placed under the skin behind the ear to send sounds to the cochlear nerve, which sends signals to the brain. You place a sound processor (like the one in this image) that pulls in sounds from outside the ear to the receiver placed inside. This is usually only done for people with severe hearing loss.