Yes. Realm is a more general term than it may sound. It really means anything that is created by magical will as opposed to formed in the chaos of Creation. They are much smaller than a universe like yours, but the space is all filled with things of purpose.

Yet, it does rely on the power of those that live within it to retain its form.

All of Arcadia is a realm, for example. Or, perhaps a few different realms linked together.