In my opinion, in my experience, dreams are usually:
The reflection of a person's inner psychological activities (the most common) can be compared with many in The Duke of Zhou.
Reproduction of broken fragments experienced during the day (usually doing things that break the usual trajectory, such as climbing mountains, doing heavy work, changing the environment, watching exciting movies)
An ominous dream symbolizes the occurrence of some major events (few, usually major changes, and the mind has a feeling)