Thanks to http://www.askyewolfe.com/Types-of-Ghosts.html
Apparitions - An apparition is the visual representation of a ghost or spirit. There are several different types of apparitions, but the mostly known form is that of seeing a transparent figure. Many apparitions look as real as any living person. Some have been known to hold conversations with people and even interact, but then will suddenly disappear. It has also been reported that certain odors have been smelled prior, during and after the sighting of an apparition. Apparitions are not limited to people, there has also apparitions seen of animals, cars, ships, trains, carriages, buildings. Simply put, an apparition is something that we see, that is often transparent, that suddenly disappears in front of our eyes or walks through solid objects like a door or a wall.
Entities - These are the most intense of infestations, and fortunately, very rare. Many people have opinions on what this final level of ghosts are - some people think they are extremely violent individuals, murderers, psychotics, and just plain evil people. I tend to believe that they are something that was never human to begin with. Strangely enough, they are almost exclusively called forth through Ouija Boards, seances, and necromancy ceremonies. If someone else called forth an entity in a home - it can remain dormant for years - even decades - until circumstances are right for it to manifest. It is patient and will wait until it can emerge at it's strongest. It feeds on anger, strive, depression, arguments, and general turmoil. It makes these emotions worse and the worse it can make the situation, the stronger it actually becomes.
Intelligent Ghosts - Unlike residual hauntings, these type of ghosts are not in a 'stuck in time' type of deal. They actually seem to have intelligence. These spirits are interactive, sometimes verging into the territory of the poltergeist. They may try and attract your attention by creating odors, moving things, making noises such as footsteps, slamming doors, or moving and hiding objects.
Poltergeist - The word poltergeist usually brings with it the fear of angry demons or“angry ghosts”. Poltergeists have been traced to psychokinetic activity of living under stress, referred to as RSPK, recurrent spontaneous psychokinetic activity by parapsychologists. It is the unconscious release of stress into the living environment of someone who can not release the stress any other way. At times the release is due to the relief of stress (arguing, yelling, difficult situations). The person causing these things is usually not aware they are causing these things to happen. Events surrounding poltergeists include; movement of objects, disappearing and reappearing of objects, electrical disturbences, water coming from no apparent source, objects raining down from the ceiling or from outside (rocks from no apparent source), apparitions, smells (usually unpleasant), and small spontaneous fires. Poltergeist activity is usually short in duration, as little as a few days or few weeks. They are usually thought of coming from children going through puberty, but can happen to anyone at any age. Residual - Residual Hauntings are "recordings" of an event in time that are left at a location, that are played back at a later time. You may hear residual hauntings on tape recordings or see them, endless loops of the same scene being played over and over, and they are usually always experienced in the same location. A couple ways these impressions are left on a location is: A traumatic event happening at the location, or by someone doing an action over and over at a location, causing it to be imprinted there. A traumatic moment in time leaves an indelible impression on a building or area, one example being Battle Fields. There are numerous accounts of people seeing soldiers fighting battles on old battle fields, only to learn later that day that there were no reenactments going on that day. By someone doing an action over and over in an area, they can leave an impression on the location also, example being: when people hear footsteps walking down hallways yet no one is there, or when people see apparitions walking up/down staircases. Another example of this is: In St. Augustine, Florida there's been a apparition of a woman who, every time seen, is always in the same location, and always doing the same thing. Her laundry, as if she is stuck in time.
