Description is the part of dreaming that makes dream interpretation possible. If you have a dream but you cannot describe it to someone after you have had it, then how can they help you understand what the symbols might mean. And better yet, how much meaning can they really hold for yourself when you are unable to even understand how to relay them to others.
Sometimes the mind picks up on symbols without you consciously realizing it. In other words your mind might see things happening that the rest of you are unable to understand or comprehend. Usually when something like this happens, you tend to sort through all of that information when you sleep.