Types of Hauntings

Poltergeists 

A poltergeist, german for noisy ghost, is the type of a haunting where a ghost is rarely seen but affects objects and people within the area of the haunting.  This is the type of a haunting where objects fly across the room, bedsheets are pulled off in the middle of the night, loud banging or noises occur in certain areas of the house and typically when one investigates there is no physical cause. 

It sometimes seems that the ghost or spirit is being mischievous and is considered more of a prankster than a danger, although none the less frightening.  In more cases than not, the events tend to center around a young teen or pre-teen child and the great majority of them tend to be female. 

There are two major theories behind the link between adolescents and poltergeists;  one is that the child is intentionally "faking" the events for attention, the other is that the child is the cause but is unaware of it.  The explanation being that the child is manifesting some type of PK or psycho-kinetic energy on a subconscious level.
In other words, the victim is somehow causing the manifestations whether they know it or not. 

Of course there is always the theory, as made popular by the movie of the same name, that a poltergeist is a conscious spirit that is for some reason unhappy with the "fleshies" that are now occupying their home space and therefore will do whatever it takes to rid them from the dwelling.

Crisis Apparitions

Crisis Apparitions are a very specific type of haunting and are usually very short-lived but very vivid.  Generally a crisis apparition is when someone experiences the vision of a close relative or friend at the instant of their death.   The apparition many times displays physical signs of the manner of death and the receiver of the vision is previously unaware of the death of the individual.  Often the time of the vision is extremely closely related to the actual time of death of the individual. 

Recurrent Event Playback

This is the type of haunting where a certain event in time (usually the tragic and violent death of an individual) is played back time and time again like a supernatural video or audio tape recorder.   An example would be the famous Tower of London in England.  The Tower of London was used, among other things, to house prisoners before their execution.  One story is that you can hear the screams of a woman and frantic footsteps every now and then.  Some believe them to be of Anne Boleyn (2nd wife to Henry VIII) or Catherine Howard (5th wife to Henry).  They say that it is possibly Catherine Howard, temporarily escaping from her guards and recaptured before her execution.  Both woman were beheaded for "treason" and "adultery" under Henry but historic documents show Anne to have been very composed and almost comfortable with her death and the legend of Catherine Howard escaping from her guards did not take place in the tower but in Hampton Court.   It is not so much important, the identity of the ghostly phenomena, as the occurrence itself.