These may have a physical, psychological or metaphysical origin and may relate to the superconscious, the subconscious or the conscious minds.  Thus, they can be incoherent and meaningless, or they can be significant.  The latter will often follow a ‘dream sequence’ and so it is advisable to keep a record of them; then reference can be made to them later, to discern whether there is a pattern.  Individual dreams are often fragments of whole, like pieces in a jigsaw puzzle, meaningless on their own.