facial expressions and tone of voice are two nonverbal signals that are relatively easy to recognize when someone is communicating with you.
facial expressions can convey a wide range of emotions such as happiness or sadness or anger or surprise and they can be used to indicate interest or boredom or confusion.
tone of voice can also convey emotions and attitudes such as enthusiasm or sarcasm or irritation.
by paying attention to these nonverbal signals you can gain additional information about the speakers thoughts and feelings and intentions and you can adjust your own communication accordingly.