What Are Dreams? A Nova documentary presented by Jamie Effros which goes in-depth into this common yet largely unexplained phenomena.
A dream is what you hear and see when sleeping, sometimes they can resemble real life and sometimes they can be something completely different. Most people have no control over the contents of their dreams the majority of the time, however, others are able to manipulate the narrative structure of the dream, known as “lucid dreaming” which is where the subject can sustain a certain amount of cognitive awareness.
There are a lot of theories about why people are able to dream and what the purpose of them is as we see in the documentary “What Are Dreams?”. They could be an evolutionary trait of humans allowing us to make decisions based on the past and future as many people say they have dreamed the same narrative over and over again like a subconsciousness trying to tell them something.
Another interesting aspect of the REM cognitive mode is how sometimes one can recall a dream they had immediately while others are completely forgotten after waking but may be recalled in clarity hours, even days after.