In some cases, more often in regular speech, delivery or body communication can contradict the message or spoken word of a speech.
For example, you and your sister get in a fight over a seat at the dinner table and who is to sit there. The fight escalates, and your mother has to step in. She tells you both to apologize, seeing that both you and your sister were in the wrong at some point. You deliver a well said sorry to your sister, along with a genuine expression of guilt and remorse. However, when it comes time for your sister to apologize, the apology is said, but with a side eye and a hint of anger. Her arms are still crossed and a frown is on her face while she avoids eye contact with you after.
Now, this is a silly, maybe based on my own life, not necessarily speech, but it represents the foundation of body language and delivery in the true meaning of spoken words. A speaker can say one thing, and on paper it would appear to be a genuine statement. However, given the opportunity to observe the physical actions and to hear the tone of the speaker's voice can change the perception of the spoken word all together.
The sister in the example was not genuinely sorry. Though she said sorry and said how she was wrong, her facial expression, her arms crossed, and her tone of voice all pointed to an unsaid feeling of anger that was still there.