A ghost is a dead soul. They wander in and out of the underworld, but they have no physical form. So when we read the Tibetan scriptures, these ghosts may feel uneasy or afraid, and thus appear in our dreams.
However, this does not mean that we have met a ghost or something terrible. Ghosts are just illusions in our hearts, which are caused by our fears and anxieties. Therefore, we should keep calm and not be intimidated by ghosts. Instead, we should read the Tibetan scriptures more firmly and constantly strengthen our beliefs and practice.