Do you believe in ghosts and why?

I saw something one night. I don't want to say it was a ghost, because it had an outline, something like a strip of energy with specks of colored lights inside the strip. Inside the strip of energy it was dark. The shape appeared to be that of a human male, with a large beak of a nose, a deep chest, and a wasp waist.

It walked through the closed door from the basement, across the hallway, and into the bathroom.