The human brain is a mysterious mass of neurons. We are still not clear about how and why it operates like it does. The question of whether dreams actually have a physiological, biological or psychological function has yet to be answered.

Sleep consists of two parts: rapid eye movement sleep (REM) (துரித கண் இயக்க தூக்கம்) and non rapid eye movement (NREM) (துரித கண் இயக்கமல்லாத் தூக்கம்). During about eighty percent of your sleeping hours, you are in increasingly deep stages of NREM sleep, during which time your heart rate and breathing become slower and more regular and your cerebral cortex (பெறு மூளைப்புறணி) —the outer shell of the brain—is dominated by high voltage, slow-wave activity (உயர் மின்னழுத்த மெது அலை).

Dreams work hand in hand with sleep to help the brain sort through everything it collects during the waking hours. During the day your brain is met with hundreds of thousands, if not millions of inputs (புறத்தூண்டுதல்) each day. Some are minor sensory (உணர்வு) details like the color of a passing car, while others are far more complex, like the powerpoint presentation you're putting together for your job.  The cerebral cortex is the largest structure in the brain and is associated with these thoughts and actions. During our waking hours it is actively involved and its electrical activity is low voltage (தாழ் மின்னழுத்த வேக அலைகள்) with very fast waves,"—the opposite of its activity during NREM sleep.

During the day, our brains is required to work hard to make connections between neurons to achieve certain functions. When posed with a task your brain is totally focused on that one thing. When you are taking a math exam, the brain is totally focused on maths. If you are chopping vegetables for cooking, your brain is focused on making the right connections to allow your hands to work with a knife, and other implements,to make an exact cut. The same goes for simple tasks like hitting a nail with a hammer or more complex tasks such as repairing a computer. During these activities connections are being made and unmade constantly between the neurons in our brains. If your brain is not focused you will not be able to complete the job you have taken up. Have you ever lost focus and cut your finger while chopping vegetables because your mind was elsewhere?

During sleep the brain is not required to focus on anything. Therefore during sleep  the emotions of the day battle it out in our dream cycle. REM sleep gets its name from the rapid eye movements that are present during this phase. Though you are sleeping, the cortex is in an awake-like state, dominated by low voltage, fast-wave activity. REM sleep is believed to be the most active period for dreaming. During sleep, the brain works through all of the information collected during the day to decide what to keep and what to forget. Dreams play a role in this process.

You may be dreaming that you're flying through the air, Or that you're being chased by a gang of goondas. Or perhaps you're chatting with a long-dead family member. If something is weighing heavily on your mind during the day, chances are you might dream about it either specifically, or through obvious imagery. For instance, if you're worried about losing your job to company downsizing, you may dream you're a shrunken person living in a world of giants, or you're wandering aimlessly through a great desert.

When one clear-cut emotion is present during the day, dreams are often very simple. Thus people who experience trauma--such as an escape from a burning building, an attack or a rape--often have a dream something like, "I was on the beach and was swept away by a tidal wave." It is obvious that the dreamer is not dreaming about the actual traumatic event, but is instead picturing the emotion, "I am terrified. I am overwhelmed."

When the emotional state is less clear, or when there are several emotions or concerns at once, the dream becomes more complicated. In such instances, when you are going through a number of events in a day dreaming activates and reorganizes the recent experiences.

NREM sleep is involved with  memory and learning and  REM sleep may be involved with creative problem solving. REM sleep allows the brain to work creatively on problems posed before sleep. Anyone who has tried to learn new material trying to keep awake beyond 1 am knows that such material is not retained and "evaporates". On the other hand material that is learned just before a good night's sleep is  almost always retained. Thus dreams have a major role to play in improving memory and boosting performance.