This film it's about your fears and your imagination.
Sometimes the way you project your fears in your head you may project them with such a huge intensity that your fears actualy become "real" to you, in a way you cannot get rid of them.
Your paranoia creates a false reality making that false reality be part of your life and your imagination keeps seeing things that aren't real.
There are several stories in this movie all of them talks about a different fear but deal with them the same way.
In each storie a different drawing style it's used all in black and white giving them a sensation of darkness.