An accommodation type, or room type, can for example be named “Single room” or “Double room”. It holds the room description, number of guests it can accommodate, price etc. Your property might have many rooms under the same accommodation type. So multiple rooms (accommodation units) may be associated with one accommodation type.
Go to Settings->Accommodation typs and create a new.
If you want to Edit an existing Accommodation type, click on "Edit" under the type you want to change settings for.