Paranormal experts point to several reasons that any one particular place might be haunted. According to them, spirits may be stuck between two planes of existence, or a spirit may be a mere recording of a previous event. Spirits may be messengers from beyond, visiting to help the living.
In the case of residual hauntings, spirits may be reliving some sort of emotionally charged event or trauma that occurred. This type of spirit doesn't interact with the living or even seem to be aware that the living are present. There have even been residual remnants of trains and cars that have been reported in the physical world.
Other theories hold that some spirits are actually poltergeists that have the ability to interact with the physical world by slamming doors, turning on lights, and even scratching the living. Some experts suggest that poltergeists were never living beings at all, but instead are demonic in nature.
Skeptics who do not believe in the existence of spirits believe that so-called spirits are actually projections. From this point of view, a ghost haunting a town hall or other building does not exist but is a projection that is made up in the mind of the person seeing the spirit. Some skeptics believe that people even have the ability to project these images of spirits for others to see as physical manifestations that are not based in reality.