Also refereed to as "Worlds."
These are separate worlds, each with its own structure. The whole of the Divine Continent and its Subsidiary Realms would be considered one very tiny Domain. These separate worlds are not limited by the Power of Law such as the Divine Continent either. At the same time, The Divine Continent itself is one of 3,000 Subsidiary Domains of the Draconic Ruins Realm, which in turn is part of the 3,000 Greater Realms.
In his past life, Nie Li was able to break through the limitations of the Power of Law on his own and visited many other worlds, including the Draconic Ruins Realm.