According to Sigmund Freud, dreams are symbolic descriptions of unconscious
desires. In effect this tells us that dreams have meanings, but these meanings
are not what they seem.
To give substance to this theory, one has to specify rules for converting unconscious desires into dream stories, and back again. Since there is no independent way to discern the particular unconscious desire lying behind any given dream, there is a tendency for self-appointed dream interpretation experts to make it up as they go along.
For further details, consult one of the many dream dictionaries that can be purchased at your local bookstore.