Dreams represent two things
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Haribol

If the activities of pure consciousness are stopped, certainly the conscious living force will be otherwise engaged because unless engaged the consciousness has no standing. Consciousness cannot be silent, even for a moment. When the body does not act, the consciousness acts in the form of dreams. Unconsciousness is artificial; by induced extraneous help it remains for a limited period, but when the intoxication of the drug is finished or when one is awake, the consciousness again acts earnestly.
Purport SB 3.6.36

There are different procedures and rules and regulations which are followed in temples of Viñëu, and devotees go there and see the Deity, the vigraha, and spiritually enjoy the form because all of the Deities are benevolent. The devotees express their minds before the Deity, and in many instances the Deity also gives answers. But one must be a very elevated devotee in order to be able to speak with the Supreme Lord. Sometimes the Lord informs the devotee through dreams.
-Purport SB 3.25.35

Our creation of friends and enemies within this material world is something like dreaming at night. In dreams we create so many things out of various impressions in the subconscious mind, but all such creations are simply temporary and unreal. In the same way, although apparently we are awake in material life, because we have no information of the soul and the Supersoul, we create many friends and enemies simply out of imagination. Çréla Kåñëadäsa Kaviräja Gosvämé says that within this material world or material consciousness, good and bad are the same. The distinction between good and bad is simply a mental concoction. The actual fact is that all living entities are sons of God, or by-products of His marginal energy. Because of our being contaminated by the modes of material nature, we distinguish one spiritual spark from another. That is also another kind of dreaming.
-Purport SB 4.9.33

Similarly, in dreams also we create many false things out of imagination. A self-realized person, or a devotee, knows well that this material cosmic manifestation is a temporary, illusory representation appearing to be truth. It is like a phantasmagoria.
-Purport SB 4.12.15

In dreams we sometimes see things that we have never experienced in the present body. Sometimes in dreams we think that we are flying in the sky, although we have no experience of flying. This means that once in a previous life, either as a demigod or astronaut, we flew in the sky. The impression is there in the stockpile of the mind, and it suddenly expresses itself. It is like fermentation taking place in the depths of water, which sometimes manifests itself in bubbles on the water's surface. Sometimes we dream of coming to a place we have never known or experienced in this lifetime, but this is proof that in a past life we experienced this. The impression is kept within the mind and sometimes becomes manifest either in dream or in thought. The conclusion is that the mind is the storehouse of various thoughts and experiences undergone during our past lives. Thus there is a chain of continuation from one life to another, from previous lives to this life, and from this life to future lives.
-Purport 4.29.34 (this one is significant for me for often I have have very powerful flying dreams)

Sometimes in a dream we see something never experienced or heard of in this life, but all these incidents have been experienced at different times, in different places and in different conditions.
PURPORT
In the previous verse it was explained that in dreams we see that which was experienced during the day. But why is it that we sometimes in our dreams see what we have never heard of or seen at any time during this life? Here it is stated that even though such events may not be experienced in this life, they were experienced in previous lives. According to time and circumstance, they combine so that in dreams we see something wonderful that we have never experienced. For instance, we may see an ocean on the peak of a mountain. Or we may see that the ocean has dried up. These are simply combinations of different experiences in time and space. Sometimes we may see a golden mountain, and this is due to our having experienced gold and mountains separately. In the dream, under illusion, we combine these separate factors. In this way we are able to see golden mountains, or stars during the day. The conclusion is that these are all mental concoctions, although they have actually been experienced in different circumstances. They have simply combined together in a dream. This fact is further explained in the following verse.
-Verse and purport SB 4.29.67

The activities of the living entity in the body of a dog may be experienced in the mind of a different body; therefore those activities appear never to have been heard or seen. The mind continues, although the body changes. Even in this life-span we can sometimes experience dreams of our childhood. Although such incidents now appear strange, it is to be understood that they are recorded in the mind. Because of this, they become visible in dreams. The transmigration of the soul is caused by the subtle body, which is the storehouse of all kinds of material desires. Unless one is fully absorbed in Kåñëa consciousness, material desires will come and go. That is the nature of the mind—thinking, feeling and willing. As long as the mind is not engaged in meditation on the lotus feet of the Supreme Personality of Godhead, Kåñëa, the mind will desire so many material enjoyments. Sensual images are recorded in the mind in chronological order, and they become manifest one after another; therefore the living entity has to accept one body after another.
-Purport 4.29.68

Hare Krishna Bhaktin Jess!
A very nice question asked! Different people have different opinions about dreams. It does not have an exact defenation.
God has given human beings the gift of 'mind'.The mind has three parts- conscious, sub conscious and unconscious.
Dreams represent a world of imagery in which our darkest fears, deepest secrets and most passionate fantasies break out from the unconscious mind and only at that time become present to our own consciousness.
Our mind is very powerful and sometimes it shows us things which are likely to happen in the future. These are known as 'intutions'.
There is a difference between dreams and intutions.Only a well trained mind can find out the difference between them.
Well, mind is so powerful that if used to it's maximum capacity then sky is the limit! The sages and saints in the ancient times controlled the mind power by meditating. By doing this, they could see the past, present and future and also link with the Lord!
Conclusion by me is that dreams are the mind-games!
Hari Bol! :)