According to this theory, ghosts are recordings of past events in certain surroundings, energy that is trapped somewhere in the time continum and allow to play again events that were emotionally "charged", to living people sensitive enough to discern them.
Although most agree that these types of apparitions do appear to be "recorded" somehow in the surroundings, there is disagreement on how exactly we as observers perceive these recordings. One side postulates that it is something within the observer that sets the recording in motion, and that the recording thus "plays inside our heads." The other side postulates that the recording is being played externally for all to see, but that only those with the right "gift" can experience it.
We know from science that everything is composed of energy. Our thoughts, feelings, sensations, experiences, and indeed our very souls are all forms of energy. The theory is that when the physical body dies, this energy continues on in some form and can be tapped by living persons sensitive enough to perceive it.
Thus, as frightening as this type of manifestation may be, the apparition is not a thinking entity, nor does it have a will or a purpose, and it is no more of a threat to the observer than watching a character on a television show.