The body is a community of cells working together to create a more meaningful kind of being than any number alone or in perfect synchrony could. The fundamental process of time is a contrariety complementary to the breaching the continuity between cause and effect, and between logical antecedence and consequence, as the most rigorous term of that continuity. That is, each cell in the body is busy making itself the most differentiated and therefore most efficient nexus of the community in contrariety to mere replication it is. But each cell requires time every day to attend to its inner workings, like storing sugar. And so we sleep. The mind serves itself in this time, or part of it, practicing the means of apperception as the middle term between reason and perception. People who get ample sleep live healthier, longer, and more mentally acute lives. Einstein famously slept eleven hours a day. Sleep is necessary, but hardly an evil. It is only an evil to those who regard time itself as an evil that must be filled with "beneficial" activities that reseal the breach of its continuity. It is the Calvinist myth that "idle hands are the devil's workshop". If you believe in transcendence time is corrupt, and not to be indulged by leisure or sleep.

In the podcast, the question was posed by Ken Taylor to the guest Deirdre Barrett as to what the evolutionary value of dreaming was. And while I would not, given her expertise in the field, dismiss her explanations, I would, humbly, offer a couple of my own.
The first, which is less evolutionary and more existential, has to do with the concept of intentionality as it was embraced by Husserl and Phenomenology: the notion that consciousness is always consciousness of something. And if we follow the reasoning through, we realize that in order for something to be conscious, it has to, at bottom, recognize that it is conscious. But as Barrett points out, there are points, at our deepest level of sleep, at which consciousness just dissipates: its very nothingness and non-being. And it would make perfect sense for consciousness to resist this while the body requires it. Therefore, consciousness has to ease into it (dip its toe into the water), via dreams, by immersing itself step by step. This is why, for instance, while we fall asleep, we tend to experience our thoughts suddenly projecting into the visual and often find ourselves jolting into full consciousness because of something jumping out at us. That jumping out basically represents the possibility of consciousness? non-being. This, for me, always brings to mind a quote by an old man in the movie Moonlighting:
?I hate sleep! It?s too much like death.?
 The second, which is more evolutionary in nature, has to do with brain plasticity. Here we have to look at dreaming as a kind of mental bricolage in which the mind and brain (via consciousness (does a kind of random psychic inventory in which it goes through its contents (its memories, its emotions, its knowledge, etc. (and randomly fuses them together until it finds patterns that resonate with it that it then stores so that it can play those patterns off of other random mental units. In this aspect, it makes perfect sense, as Barrett points to, that many of our greatest minds would turn to dreams for inspiration. But I would argue that it is a little more fundamental and democratic than that in that dreams are the process by which the brain (via brain plasticity (improves the underlying structures of how we think so the mind can move to the next level. This would explain, for instance, why less creative people tend to claim to not dream.

We can learn a lot by considering the special discipline of remembering our dreams. It is a difficult matter because dreaming has no past or future tense. It is immediacy. You cannot remember dreams so long as you are bent upon time dispersed into its tenses. Only now is it anything at all. You can't go back or plan forward. This makes consciousness unfit material for phenomenology. As Sartre shows in his two early works on the imagination, the intentional object is sustained as the image, not as the percept, of consciousness. In fact, perception is not a constant observance, it is a narrative of many moments and of growing moment. The watching eye is never still. The phenomenon is a construct of a dialectical tension between faith and reason that becomes quaint or anachronistic where the historical role of faith recedes. That's why nobody talks about Husserl anymore, the role of the phenomenal in overthrowing superstition is thought to be achieved and his methodology obsolete. But what does sustain consciousness as phenomenally real is its responsiveness, both to stimuli and to its own reasoning. If some people claim not to dream this only means they have neglected the art of remembering that they do dream. It is not an easy matter to separate our perceptions from the division of time into tenses. And what sustains consciousness is not such separation and reconstruction/deconstruction, it is the narrative unity of growing moment in the power to be responsive, as responsive to external stimuli and perception as to reasoning. But the easiest pitfall is to suppose mind phenomenally distinctive, when in fact it is organic. You cannot distinguish the mind from the community of cells the organism as a whole is and into which it is the hub of a constant and intricate array of sense. Your fingertips are as much a part of your mind as your frontal lobes. And if sleep at any stage is thoroughly null, how is it that, however deeply asleep I may be, I can answer the phone before my machine does, and can clearly identify what had just gone 'bump in the night' and so woken me? The power to respond in sense, by sensing and answering sensibly, is not nothing even when it drops its "intentional object" in favor of giving the rest of the organism a breather.    

I am very into lucid dreaming, and am currently reading a book called 'dream yoga'. While lucid dreaming itself is quite amazing, once one is able to often become conscious in dreams, many psychological explorations open up to the dreamer. In lucid dreams, there are skills that can be developed, wonderful experiences to be had, and learning can take place.

2 things are necessary to start ones journey to becoming an oreironaut (dream explorer): begin a dream journal to help with remembrance of dreams, and perform reality checks in waking life where one questions "is this real or a dream" until it becomes habitual. My favorite reality check involves plugging my nose and trying to breath in through it while i question reality; in waking life, you cannot breath in with your nose plugged, but in the dream world you can!

Ancient Tibetan Buddhist philosophies teach of the mind-body connection, exploring our subconscious, medatation in dreams, and even changing our waking perspective.

The movie Inception mentions the people that fill the dream world as projections. A trick i learned is to find or summon a phone inside the dream and press 0 for operator. The 'person' on the other side of the line is there to assist any problems one may have in the dream world: escaping nightmares, explaining subjective meanings, granting in-dream powers, anything one needs.

"Have you ever had a dream you were so sure was real? What if you were unable to wake from that dream? How would you know the difference between the dream world and the real world?" - the matrix

https://animals.mom.me/octopuses-sleep-2969.html

The brain reviews events and and refines learned behavior during dreams. A person will generally perform a newly learned task better after a good nights sleep. The hypothesis has been tested and proven using test subjects and video gaming.