There are believed to be different types of ghosts. The two major types that are commonly found are either a "real live dead guy" or a sort of "recorded haunting". The difference between the two is pretty simple - one has conciousness and one does not. The recorded type is thought to be merely a record of some traumatic or overwhelming event that happened in a certain place. Like the spirits you hear of that walk down the same hallway, or up the same steps, the same time of night/or the same time each year. If you were to step in front of this ghost, it would continue on it's merry way, oblivious to you, because it's simply a playback of a past event. Like a vcr tape.
The "RLDG" theory holds that the active soul has not gone on to whatever afterlife there is for some reason (perhaps boredom, like me probably one day?). It still has conciousness. Take the scenario I mentioned. If you were to step in front of THIS type, it may choose to ignore you OR it may stop, look at you, and go around you (for example).
Ghosts tend to come in different shapes and sizes, from orbs (generally round globules of light that float and commonly come up on film), to full out apparitions (looks like the real person). There are many shapes and sizes in between, such as vortexes, rods, & mists.
Although it is not scientifically proven what they are made of, I tend to go with the pure energy theory and can't deny the ectoplasm that forms. A good site to look at is The Shadowlands (
www.theshadowlands.net - I think net) or
www.sjgr.org. I recently joined SJGR as a trainee, so I can attest that it's a pretty thorough site.
