During a dream, have you ever known you were actually in a dream?

Have you ever had the experience where you, at some point during a dream, realize that it wasn’t real and you were just dreaming? How many times has this happened to you? What was the experience like? How long did you remain dreaming? Were you able to somewhere or completely control what you were doing? Do you think it is possible that when someone experiences this that it is just you dreaming that you think you know dreaming? Could it be possible to dream inside of a dream? Is this getting confusing?