Dogs: Have a body language too.
What is your dog trying to tell you? Dogs have a language that allows them to communicate their emotional state and their intentions to others around them. Although dogs do use sounds and signals, much of the information that they send is through their body language, specifically their facial expressions and body postures.

Understanding what your dog is saying can give you a lot of useful information, such as when your dog is spooked and nervous about what is going on, or when your dog is edgy and might be ready to snap at someone. You do have to look at the dog's face and his whole body.
(Article by: By Stanley Coren).