A dream is a combination of mood(something emotional/spiritual) and visuals(something physical) and sometimes voices(words/speach)

Human = Physical + Emotions

A dream is a contact between alternative universes;through the mind (Brain),which is much superior to the body(that is why it is placed on the top...in the skull!),and it is the link to the spirit. Dreams make a human being entirely complete.

What are dreams?
If you have noticed, the events you see in a dream are recorded in your memory just like any other memory of an event which took place in your conscious past. It implies that in the vast database of your memory banks an ordinary event while awake and the events of a dream are recorded in the same manner.The only difference between the two kinds of memories is that YOU remember which one took place while you were asleep and which one took place while you were awake.
According to Richard Bach (Illusions: The Adventures of A Reluctant Messiah), dreams are events that take place in another time-space dimension, and we remember them even when we come back from that particular time-space to the present time-space of life we are living. Does it mean that we are living a life in another time-space dimension? and we often visit it in our dreams when our souls are free!?
But then sometime, some events of your waking life are so surreal/dream-like that they could have been a part of your dreams. Then again some dreams are so vivid and sad that you don't know why? and you still feel sad even when you are awake back. It is as if you went there just to bring some peaceful sorrow into this life for sometime.
Everybody does not feel the same way about their dreams...or do they?

Dr. Nexus, 1991

It is known from the Dead Sea Scrolls that the religious Essene communities of biblical times believed that sleep was a small death, and treated it with as much respect. As members of the community went to sleep there was an acceptance that they might not awaken, so when the next morning dawned it was greeted as if it were a new life, a new birth. It appears that these people made it a point to leave nothing undone or unsettled at the end of the day. All arguments had to be resolved, wrongs forgiven and quarrels settled so that each person might be released from the life-day to enter the dream-death-night. Such a way of entering sleep would mean that one is unburdened by unresolved garbage, so that dreams would be free to pick up deeper and richer threads.