Dreaming is one of the strangest ordinary things the brain does.
Every night, the brain produces images, thoughts, emotions, and stories that can feel completely real while they are happening.
Scientists know a lot about the sleep stages associated with dreaming.
They still do not have one single explanation for why dreams exist.
Dreams can happen in several sleep stages
People often associate dreams with REM sleep, short for rapid eye movement sleep.
That makes sense because REM dreams are often vivid, emotional, and story-like.
But dreaming can also occur during other stages of sleep.
The content may simply be different.
What happens during REM sleep?
During REM, the brain becomes highly active.
The eyes may move behind the eyelids.
At the same time, most large voluntary muscles are temporarily inhibited.
That helps prevent you from physically acting out most of what is happening in the dream.
Are dreams helping with memory?
Possibly.
Sleep itself is strongly connected with learning and memory.
Dreams may reflect some of the same processes as the brain reviews, reorganizes, and integrates recent experiences.
That does not mean every dream has a specific memory-processing job.
It means dreams occur while the brain is doing a lot of memory-related work.
Are dreams about emotion?
Often.
Dreams frequently contain emotionally charged situations, worries, social interactions, and recent experiences.
Researchers have proposed that dreaming may help with emotional processing, but no single theory explains every dream.
Do dreams contain hidden messages?
There is no scientific evidence that every dream contains a secret symbolic meaning that can be decoded with a universal dictionary.
Dreams can reflect concerns, memories, fears, and experiences.
But sometimes the brain appears to combine fragments into something that resembles a story only because the sleeping brain is very good at making connections.
Why are dreams so weird?
The sleeping brain is not operating exactly like the waking brain.
Systems involved in emotion, imagery, memory, and logic can be active in different proportions.
That can produce a dream where your third-grade teacher is driving a submarine through your kitchen and nobody involved finds the situation especially suspicious.
Do we dream every night?
Most people probably dream far more often than they remember.
Remembering the dream depends heavily on when you wake and what happens immediately afterward.
So dreaming is real brain activity during sleep.
Why your third-grade teacher was driving that submarine is still between you and your brain.
A related piece of human behavior appears in Why do we forget dreams so quickly?, where the brain handles another everyday judgment or response.
And that’s the short explanation.
Related explanations: Why do we forget dreams so quickly?, Do dogs dream?, and Why do we yawn?