The human brain is a mysterious little ball of gray matter. After all these years, researchers are still baffled by many aspects of how and why it operates like it does. Scientists have been performing sleep and dream studies for decades now, and we still aren't 100 percent sure about the function of sleep, or exactly how and why we dream. We do know that our dream cycle is typically most abundant and best remembered during the REM stage of sleep. It's also pretty commonly accepted among the scientific community that we all dream, though the frequency in which dreams are remembered varies from person to person.
The question of whether dreams actually have a physiological, biological or psychological function has yet to be answered. But that hasn't stopped scientists from researching and speculating. There are several theories as to why we dream. One is that dreams work hand in hand with sleep to help the brain sort through everything it collects during the waking hours. Your brain is met with hundreds of thousands, if not millions of inputs each day. Some are minor sensory details like the color of a passing car, while others are far more complex, like the big presentation you're putting together for your job. During sleep, the brain works to plow through all of this information to decide what to hang on to and what to forget. Some researchers feel like dreams play a role in this process.