There are degrees to being deaf or hard of hearing. While many people are classified as being hard of hearing, they can hear. The hearing issues they experience have to do with hearing well enough to understand the sounds. Many of them can be helped with hearing aids that sort the sounds they hear into meaningful words.
People who are deaf rather than hard of hearing experience more than just difficulty hearing words. They may not be able to recognize what the noise represents, but they can at least hear something. These people may often be helped with the use of hearing devices. Being able to hear, even slightly may make the difference between being deaf and being profoundly deaf. There are people without any hearing at all. These people are called the profoundly deaf. They can hear almost no sound at all, and their loss of hearing is so great they generally cannot be helped with hearing devices.