To help answer specific questions about presenting a speech, we will consider three major categories of nonverbal behavior that affect delivery: body language, eye contact, facial expression.
Compared with the abundant and colorful audio verbal behaviors, nonverbal behaviors are really kind of silent language, noiseless but infectious.
Therefore, whether people are speaking or not, hand gestures merit our attention as a rich source of nonverbal behavior to help us understand the thoughts and feelings of others.