Ghosts are the spirits of once living people, and when they die, they become ghosts. If they aren’t roaming the earth, they are most likely sleeping in their coffins, or possessing people or objects. Their spirits start out very strong, but the longer they stay on earth, the weaker they get. Over time (maybe a few years) they completely fade away as their life essence gets used up.

Ghosts aren't really what we think they are. We think they're spirits of the dead, when in reality that's not the case. Ghosts are real, living, people. They aren't dead, and they aren't from our world. They live on an Earth very similar to ours, except some people who are dead here aren't dead there (and vice versa.) We can see them sometimes because occassionally, the overlap between these seperate dimensions is strong. These different versions of Earth are simply overlapping, and that is why we can see ghosts.