Feedback refers to the messages sent from the receiver to the sender indicating that the original message was both perceived and interpreted.  Feedback tells the speaker the effect s/he is having on his/her listeners and can either be positive or negative (Devito 2005).

Positive feedback: the message is well-received and should be continued (smile, head nod, applause, thank-you).
Negative feedback: something is wrong with the message being received and thus an adjustment should be made (verbal criticism, puzzled expression, lack of engagement).
Person focused: centers on the person and his/her appearance or personality ("you look pretty," "you are very nice").
Message focused: centers on the message conveyed ("I disagree with your point," "Can you repeat that address?").
Immediate feedback: feedback sent right after the message (asking questions, complimenting the speaker).
Delayed feedback: feedback given sometime after the message was communicated (questionnaires and evaluations).
low-monitored feedback: spontaneous and honest (speaking with a friend without inhibiting emotions).
high-monitored feedback: responses constructed with consideration (carefully answering a question from your boss when asked your opinion about a new project).
Critical feedback: evaluates the speaker's performance and his/her message (good argument, but perhaps also discuss...).
                                                                                                                                               (DeVito, 2005)

http://www.youtube.com/watch?v=_E0hTktMIyE