Feedback - The verbal and nonverbal messages that tell speakers how they are being perceived.
Let's say, you are talking to someone and they respond to you either in a smile or a good, nonverbal, way or they say something positive. Positive feeback tells you, the speaker, you are doing fine in your communication.
Let's say your still talking to that same person. However, they respond to your conversation poorly, or in a way that you are able to tell they don't like what your talking about. This is known as negative feedback. This response helps you change your conversation to better it or the relationship between you two.
Self-feeedback is message you give yourself as you pay attention to your own behavior. Let's say you are talking to that same person now and the conversation starts to die. You then think to yourself that you must say something to keep the conversation going and not to make it awkward between you and the other you are communicating with.