HQ Rooms are designs for the various rooms in the HQ. Each one can provide different functionality for HQ's rooms.

There are 3 main categories of rooms. When a room is cleaned for the first time, it becomes a Config, which acts as a blank slate that can then have a Construction applied. A Construction determines what the room will be used for and can have multiple upgrade slots where Upgrades can be applied. Upgrades can overhaul the entire room or just add decorations and other objects. Upgrades can also add new functionality.

Check the Sim Settlements 2 Wiki for details for details on HQ mechanics.