What is a dream? How to understand and know?
First, the relationship between dreams and sleep.
From the perspective of life, we know that people dream when they sleep. The scientific explanation for this is that dreams are special stages in sleep. Modern cognitive neuroscience has found that the frequency of brain wave images is different in different stages of sleep.
At one stage, people's eyes will turn, so we call it active sleep, and some vivid dreams appear at this stage. Some people think they don't dream, others think they dream a lot, and these people's feelings are all illusions. Scientists have also studied why there is this illusion and found that it is because people wake up at different times. If people are actively sleeping when they are awake, they will report that they had a dream. Otherwise, it will tend to report no dreams.
Second, the source and function of partial dreams.
As the saying goes, there are thoughts during the day and dreams at night. Here we can see that one source of dreams comes from thinking about the content of life during the day. In other words, we think about some things during the day, but we haven't finished yet, so these pieces of thinking will be sorted out at night.