Lip reading is an extremely useful tool for people who are hearing impaired, it makes conversations super easy for them. Deaf people will watch the body, hands, and mouth of the person they are listening to, to understand what they are saying and which tone and volume they are using. The struggle with this is that many words sound similar which can start confusion. Most rhyming words can screw up someone who is lip reading, but with proper context clues the lip reader can more easily make out which words the speaker is saying. There are other factors that can mess up a lip reader such as people that talk super fast or have a lot of facial hair.
One of my best friends is hearing impaired and if his hearing aids die he tends to read our lips when we are hanging out. He doesn't use this everyday so he is not great at it but he can make most of the words out with context clues and focus. By him doing this it shows how impressive of a skill this is, it's like learning a whole nother language. You can only really learn this skill too if you are someone who is hard of hearing because you can unintentionally cheat if you try to learn and you can hear.