The Room Mapping facility allows you to assign various room types according to calculations such as ASHRAE and Part L.
Energy Simulator comes with its own room types which you specify in each Rooms properties. However, prescriptive calculations such as PartL and ASHRAE also have their own specific room types.
The software will automatically match the closest room type for you, however you can alter these manually should you need, as below:
To find more about Part L, please refer to the guidance here.