Dreams (n.): a collection of images, impressions, events, and emotions that we experience during sleep

Dreams are one of the most researched areas of sleep throughout history.  I could lay out every theory that has been proposed on dreaming as there have been countless physicians and theorists that have studied dreaming.  Throughout years of research, dreaming has been seen as a vehicle for predicting the future, a way to communicate with the dead, and a way to travel beyond the physical limits of our body.  One of the most popular physicians that we all know is Sigmund Freud, who believed dreams were the vehicle for the mind to explore unconscious feelings, emotions, and desires.

Despite sustained scientific exploration and attention – and no shortage of theories – we still don’t know the answer to the most fundamental question: Why do we dream? For all the study and attention dreams have received, it’s rather remarkable how much we don’t know about dreaming – not only about its purpose, but also about the mechanics in the brain that make dreams happen.
— Michael J. Breus

According to "the sleep doctor" himself, Dr. Michael J. Breus, we normally spend 2 hours a night dreaming in REM sleep, experiencing on average 3-6 puzzled dreams.  How long a dream lasts varies, but based on past studies, they last on average between 5 and 20 minutes.  Recent studies are showing that “dreams serve as a broad, virtual-reality model of waking life – a proto-consciousness – that instructs and supports survival and growth" (Breus).

Breus is a clinical psychologist and a Diplomat of the American Board of Sleep Medicine and a Fellow of The American Academy of Sleep Medicine.  He is the "sleep expert" on WebMD and has appeared on The Dr. Oz Show numerous times.

He states that scientists study dreams in two ways: 1. Through dream content focusing on themes, emotions, images, and events.  2.  Brain and body activity while dreaming happens.  Scientists conduct this research through a few dreaming technologies with electroencephalography (EEG) being the most common tool, PET scan, MRI, and fMRI.

Some of the most common dream subjects are: school dreams, sexual dreams, falling, being late, flying, being physically attacked, and dreaming of someone dead actually alive.  These common dream subjects have been proven to occur in people of diverse cultures, backgrounds, and experiences.  The brain to stop creating new memories while sleeping.  Scientists are currently working on discovering if digital media influences the content and themes of our dreams.