Rooms
All worlds are made up of a series of connected rooms. Usually these rooms are made up of walls.
When you first create a new world, you will be teleported to the default room. It's made up of 4 walls, a ceiling, and a floor.
To add another room, drag "Default Room" from the library into your heirarchy tree.
Room Layers
All rooms have three layers that determine what objects are rendered in front of each other.
Infinite Background
The infinite background is rendered behind everything else in the room. It acts as what others might call a skybox.
Enviornment
The enviornment is for objects in the background, but still in front of the infinite background. This is often walls of a room.
Contents
The room contents are rendered in front of everything else. This is the spot for furniture, plants, and other props. It's also where player avatars will be.