The word Poltergeist is derived from the German for 'Noisy Spirit' and it describes what a poltergeist is very accurately. Poltergeists are quite rare.
Poltergeist activity typically includes inanimate objects moving or being thrown about, noises such as knocking, pounding or banging which can often be quite severe, cold draughts, foul smells, levitating objects, and, on some occasions even physical attacks on those witnessing the events.
One notable and very well documented case involving Dr. Vladistav Bukreev in the 1970's saw showers of stones and bricks come down inside a house and the windows were smashed to pieces by the objects being flung through them by an unseen force. In this particular case, things would float through the air, and blood, water, and other liquid substances would pour from the walls and ceilings. The family concerned suffered what appeared to be bite or claw marks on their bodies and the two young girls were lifted up into the air and moved around with no apparent support.
Oddly enough, there are a number of theories by paranormal and parapsychology experts that suggest a poltergeist is not a spirit or a ghosts and a number of documented studies carried out since the early 1950s also suggest that a living person, typically involved in a stress-inducing situation causes poltergeist activity through psychokinesis or the direct influence of the mind. This person is known as the agent.
Poltergeist activity without the presence of an agent, is generally attributed to the remnants of intense emotions in a particular place.
Many believe that a poltergeist is an elemental entity and whether this is true or not has yet to be decided. Regardless of the differing opinions, poltergeists are very real and are the most destructive type of paranormal activity.