"A total description of the personality is, even in theory, absolutely impossible, because the unconscious portion of it cannot be grasped cognitively. This unconscious portion, as experience has abundantly shown, is by no means unimportant. On the contrary, the most decisive qualities in a person are often unconscious and can be perceived only by others, or have to be laboriously discovered with outside help." Jung, Carl. Aion (from The Collected Works of C. G. Jung Volume 9, Part II). Princeton University Press.
To help understand the unconscious, think of it like this: Picture a ransom note where the message is comprised of different words taken from magazines with various fonts and type. The note uses words from many sources to convey a statement. Now substitute the words in this ransom note for images - it now tells a story with a collage of images. Finally, imagine those images to be a collection of memories and emotions from your own life. That is your unconscious communicating to you in your dreams. It can only use what you make available to it. So it's speaking to you, through you (because it is you). Sorta like how Bumblebee in the Transformers movie uses a collection of snippets from radio station broadcasts to communicate with the humans.