>>1919310
The connecting hallways are the segments that are procedurally generated; they may exchange with any hallway type room to connect a main room. The second is an exchangeable section of a room where it can traded with another type of layout (like maybe instead of a hallway being there it could instead be a large room, circular room, another type). Just think opening a door in a room but going to a different room, while in that room, instead of going to a hallway to a room.