What should we note through the definition proposed by I. A. Malandro, et al.?

What should we note through the definition proposed by I. A. Malandro, et al.?

One should note that, first of all, nonverbal communication is used to convey messages to others and receive messages from others.
Secondly, nonverbal communication is a process of communication by means of nonverbal behaviours. Thirdly, nonverbal communication may convey messages alone or is used in combination with verbal behaviours to convey meaning. And lastly, nonverbal communication occurs in a given situation or context and is interpreted in relation to that situation or context.