1) The discarnate soul of a deceased human being or animal still occupying the physical realm. These spirits may or may not know that they are dead. They can also be called forth.
3)A demon, angel, saint, or Christ Himself.
There are actually many kinds of ghosts, but to name them all and give definitons would be impossible, due to a limit of space.
The kind of human or animal ghost that is an actual sentient being is called an apparition. Many of these beings are restless because they do not know that they have passed on due to unexpected events that ended their lives, or believe they have unfinished business to attend to. Many occupy places they frequented during life. Some do know that they are dead, and may come back for reasons of revenge, or to comfort or warn a loved one of some kind of impending disaster, or to lead them to some fortune or treasure. Others just like to hang around and see what's going on with other people. The ghosts who do the same things over and over again are the ones who don't know that they are dead, and are actually prisoners of their own minds: It may be the year 2006, but in the mind of the ghost of a person who died 100 years ago and didnt expect or realize it, it's still 1906 and he's still trying to perform whatever action he was preoccupied with when he died. They can also be called forth by seances and Ouija boards, but you better know what you're doing when you call forth a spirit. If you're poorly prepared, if not at all, you could bring upon yourself some really weird and terrifying results that will not go away. It has happened, people.
2)A residual is a ghost that has no intelligence behind its actions. It acts just like a ghost trapped in its own mental prison of time, the difference being that a residual is psychic energy imprinted on the fabric of time and space, stress being the factor that does the impression. In the mind of the person who was performing the action at the time, whatever it might have been, that action, or the situation the person may have been in at the time had some kind of significance to him, and his stress levels may have been up enough to leave an imprint of that certain event or situation. You could call it a
3)Everyone knows about haunted houses. Not only human spirits can haunt houses, locations or anything, for that matter. Demons can too. In fact, Houses with the strangest and most terriying hauntings are probably infested with demons. People who have died from things going on in the houses they lived in that were haunted were more than likely murdered by a demon, either directly or by someone else who was demon-possessed. Human ghosts haunting a house can be influenced by a demon haunting the same house to kill or otherwise harm the living inhabitants.
Manifestations of angels, Jesus, the Virgin Mary or a saint can also be called ghosts, but the proper term for these holy manifestations is apparition.
4)A poltergeist is not really a ghost at all, most of the time. While there are accounts of genuine spirits throwing things about, making noises, writing on walls or what have you, most of the time a poltergeist is nothing more than a subconscious manifestation of telekinesis, or the ability to manipilate matter with mental energy alone. This can ahppen when a person is under tremendous mental turmoil or stress. If there is no outlet for this negative buildup of mental energy, the next thing you know the lamp is flying across the living room, and smashes into the wall. This also happens when children enter puberty. It doesn't happen all the time, but when it does, it scares the shit out of everyone.