Gestures, hand movements, body postures. They all give out important nuances about one’s character. Whether you are confident or jittery. Whether you know what you are saying or just saying whatever crosses your mind.
In our psychology class, we were always told to observe. To listen through our eyes. Seems difficult and absurd, but really is integral to your personality. Your actions, your behavior cannot be replicated by someone. Mute the conversation and yet you can understand so much by the kinesthetics.
Gestures also are an important aspect of dance. Indian classical like Kathak and Bharatnatyam rely specifically on them. They create an aura of elegance and passion.