Some people believe that when people die, there's a wonderful light as bright as the sun, but it doesn't hurt to look into it. All the answers to all the questions you ever want to know are inside that light. And when you walk to it, you become a part of it forever....
And then some people die, but don't know that they've gone. Maybe they didn't want to die. Maybe they weren't ready. Maybe they hadn't lived fully, or they'd live a long, long time and they still wanted more life. They resist going into that light, however hard the light wants them.
They just hang around. Watch TV. Watch their friends grow up, feeling unhappy and jealous. Those feelings are bad. They hurt.
And some people just get lost on the way to the light and they need someone to guide them to it..."
-Dr. Lesh (Beatrice Straight), explains the afterlife to Robbie Freeling (Oliver Robbins) in Poltergeist (1982)