Lipreading is a skill that people use when there is a lot of noise that impairs your ability to clearly hear the words that people are saying to you. If other sounds obscure the sound of speech then you will find that you are unable to understand what people are saying to you using your hearing alone. In these circumstances being able to look at the lips and facial movements that the person who is speaking is using gives you vital extra information that lets you fill in the gaps and gain an understanding of what they are saying. In extreme conditions you do not just use lip reading to fill in the gaps, it becomes the main method by which you understand and interpret peoples speech.
A hearing loss impairs your ability to hear, and when your loss is severe there does not have to be any significant external sound in order to create a situation where you can not understand dialogue. The worse your hearing, the more useful lip reading becomes as a life skill that lets you live your daily life without impairment.
A lipspeaker is someone who is practiced in conversing with lipreading people because they understand the basic rules that make lipreading an effective form of communication.
