Stella, ghosts can be called Astral Entities. They exist on the astral level or demension.
also vampires are similar. Not the ones we think about. But because "blood" has power in it, these astral beings feast on that, the energy.
I've had slight cases of Deja vu. But, what is weird is that twice in three years I have awakened in a night time paralysis, and notice a huge beetle like bug on my back, I'm talking HUGE. it has it's proboscis in my back, and it seems to be the reason for the paralysis. The first time it was black, the second time, white. I've always thought it was some sort of manifestation of my mind to explain the paralysis, a kindof nightmarish reason why I can't move.
Also, I used to go to my grandfather's grave and talk to him and ask for advice, one time it was about this woman that I met at work and talk to every now and then. Two weeks after I talk to him about her, she shows up out of the blue--and after that, she would show up every so often in a weirs type of way.