Verbal communication relies on the use of words, written and unwritten, to convey a message. Verbal messages are conveyed in a linear fashion, with a clear beginning and end, based on sentence structure. We almost always use a conscious plan to deliver verbal communication. We choose the words we wish to convey, even if they don't always come out exactly the way we intended, and are conscious of choosing to speak or write to deliver a particular message.
Nonverbal communication is much more complex. Instead of using words, we utilize many different techniques to convey information nonverbally. We may gesture with our hands, stomp our feet, or make particular facial impressions that convey a certain meaning. We may also demonstrate a willingness (or unwillingness) for physical touch during communication by shaking hands, rubbing someone's cheek, patting a person's back, or giving a high five. We may make or avoid eye contact with a person, or we may distance ourselves in ways that connote warmth or coldness.
We may not even speak at all, choosing silence to convey a message. Many of these forms of nonverbal communication are not planned—at least not to the degree that verbal communication is. Unlike verbal communication, we may not even be aware that we are delivering a particular message through our nonverbal communication cues, and these cues may conflict with the verbal message we had planned to deliver. For example, I might tell a student (verbal communication) that I am happy to see her, but if I do so while avoiding eye contact, rolling my eyes, crossing my arms, and maintaining a great physical distance from her (nonverbal communication), she isn't likely to believe my verbal message.
We rely on the combination of verbal communication and nonverbal communication to effectively discern intended meanings in the interactions we engage in each day.