Many people say that they see a string attached to them and connects them to the body. If that string should break, then the person would lose contact with the body and be unable to reenter. There are people that can have a out of body experience at will.
These travelers are able to fly great distances and through walls and other objects. There have been reports of people visiting not only other homes and cities, but outer space and other realities. I have read reports where a person wakes up to find themselves in another version of themselves. There are also reports of strange and other worldly dimensions.
While uncommon, people have also seen other beings who reside in the non-physical plane. Some are helpful or reclusive and others are scary and violent. There are worries by some of their body being inhabited by one of these beings should the soul or spirit stray too far from the body. There are many techniques that people to use to create the out of body experience, but it they all generally all involve meditation and visualization techniques.
The out of body experience is closely linked to the near death experience and may simply a different form of the same phenomenon.