Dream analysis was the practice of determining the hidden meaning of one's dreams. People who appeared in one's dreams could indicate something about the individual in question.
As of 2370, Data had been studying dream analysis, lately in an attempt to understand his own dreams. (TNG: "Phantasms") He noted the possibility that Lwaxana Troi might be dreaming in metaphors, rather than literally. Deanna Troi concurred, suggesting that her seeing a child, namely Hedril, might indicate vulnerability in Lwaxana, something in her memory that she wished to protect. (TNG: "Dark Page")