Dogs can't read lips but can get charades
If you chatter away at your dog, he can't understand the vast majority of what we're saying. Dogs might be able to deduce what a few key words mean — walk, treat, toy, off — and maybe even learn hundreds of words - but they can't understand human language.
What your dog relies on to understand you is your body language. Dogs have evolved to become expert readers of the human body and can figure out what you're thinking and feeling before you do. But you can easily send mixed signals if you are only paying attention to what your mouth is saying and not your body language.
For instance, telling your dog to "stay" while leaning forward toward the dog and holding out your hand like a traffic cop can actually can be confusing for your dog.
Spend a whole day with your dog without uttering a word. Communicate only with your body. Go ahead. Try it. You will come to realize how involved a conversation can be with your dog without saying a single word.
Excerpt from this source: https://www.treehugger.com/things-humans-do-that-dogs-hate-4864319