Psychologist Freud believed that dreams are the satisfaction of subconscious desires. In a sober state, people can effectively suppress the subconscious, so that those desires that violate moral customs cannot do whatever they want. But when a person enters a sleep state or a relaxed state, some desires evade subconscious checking. At this time, desire secretly emerges from the level of consciousness and expresses itself in various images. This is the formation of dreams.