Freud believed that dreams are the embodiment of people's subconscious and the guardian of people's sleep quality. People dream as long as they sleep, and when they wake up, they think they didn't dream, but they just don't remember. Dreams are divided into two parts: explicit dreams and implicit dreams. The so-called dream is "thinking day and night." Intuitively reflect people's wishes. Hidden dreams are more complicated. The reason of hidden dreams is the unconscious checking function of human consciousness, including substitution, concealment, fuzziness and so on, which really can't be explained clearly in a few words. There are many theoretical bases for why dreams can protect sleep. LZ wants to know, so I suggest LZ take a look at Freud's introduction to psychoanalysis.