On the point of psychology science, dreams are an additional product of our subconsciousness. In this manner it works when you are sleeping.
Your tired and full of impressions mind is relaxing and poor subconsciousness is trying to digest all these images, thoughts which you have taken during a day.

In its turn, through dreams subconsciousness is trying to say you something useful, essential and bossibly awful to you…Awful – because sometime you think about very bad things which is absolutely not in line with your principles and values. But nobody could restrict you from thinking, even own mind.

Do you remember that nights when you have been suddenly awoke by something you have seen in dream? These cases are most interesting and important because you open eyes in the middle of the night only if consciousness has understood what subconsciousness is saying by mysterious images. I always note all my dreams when I awoke after it. Why?

Because this is a real notice or advice from your own subconsciousness which is in times more clever then your mind.
Next part is about images of dreams and their meaning for you.