A realm is a region of the Gargantisphere served by a single game loop. It is the unit of world simulation and authoring: a realm has its own scene, its own physics, and its own avatars.
A realm is published into and replicated across the peer-to-peer network rather than hosted on a server. Its scene is expressed via the Scene Composition Protocol as a Scene Hierarchy, carried by structural and parameter streams. Nodes subscribe only to the partitions of a realm they can currently see, bounded by a Bounding Volume Hierarchy; a large or busy realm may be split into multiple seamlessly-joined sub-realms to spread load across peers.
Realms connect to other realms through portals. A visitor moving between realms is the Gargantisphere’s analogue of following a hyperlink.