I'll try to explain everything, you don't have to read this if you don't want to and can just move on. I kind of explained it all in other chapters. I'll also add stuff as I write.
There might be slight spoilers (or clues to the story) so be warned.
The real world - the place humans live in, the awake world. People living in this world will be referred to as real people.
The dream world - place you go to when you're dreaming. It's build from a couple of parts.
The hallway - one of the parts of the dream world. It's a place from which you can go into anyone's dream.
A dream door - a door that connects your dream with the hallway. It dissappears when you wake. Every person has their own door.
A dream compass - a tool that allows user to find a specific dream door, it also shows you who's dream you're in.
To dreampass - to trespass into someone's dream. Only a few real people can dreampass, but it comes with a price. (This is cringy and I don't know why I made it.)
The middle ground - place when the dream world meets with the real world. Anyone can access it through the real world side with enough practice, but only a few can reach the other side. It's one of the parts of the dream world.
The barrier - a wall separating the real world and the dream world, basically a line between what's possible and what's possible only in your dreams. Real people can't go through it, but legends say that some might try and succeed. Once you cross it there's no turning back.
Nightmare Knight - it's a legend moms use to scare their children, but few people say it haunts them in their dreams. In reality, he feeds on negative feelings and sucks energy out of people. To do that he creates nightmares.
The order of the black crow - its beginnings can be tracked down to ancient times. No one can remember if its members are real or not because most of what was known about it was burn with the library of Alexandria. Its job could have been protecting people from Nightmare Knights and other dangers of spiritual world. Historians believe all of that could not be possibly real or survive to modern day. Could it?