Apparitions are the visible manifestations of spirits or ghosts. They are clearly visible to the naked eye, and in the case of ghosts, most often appear as the person did in life. Apparitions are connected to many different types of hauntings, and sometimes appear to act with intelligence, while at other times they simply reenact the same event over and over.
They can appear suddenly, and just as quickly disappear. Many photographs and videos claiming to show ghosts are images of apparitions, although the veracity of such evidence is often in question. Some parapsychologists believe that ghostly apparitions are, in fact, seen on the level of human consciousness, and thus ghosts and spirits would be impossible to photograph--just as we cannot photograph a thought.