Subworld

A subworld is a collection of matter within a limited area. Subworlds are similar to worlds, both containing matter. The difference is that the matter within a subworld is enclosed within a large, but limited area. This means that subworlds are finite, compared to worlds, which are unimaginably infinite in size.

A subworld can be "connected" to a world, allowing anyone in a world to access the subworlds connected to it. Subworlds can also be connected to each other, allowing anyone within those subworlds to access the subworlds connected to it. Together with worlds, subworlds make up a universe.

Types
Subworlds are also referred to as other terms, depending on the size of the subworld. There are two types of subworlds:

Realms are the largest type of subworlds. They are impossibly large to comprehend its size, although these subworlds are still finite in size.

Dimensions are the smallest types of subworlds. Their sizes are always known and are much smaller than Realms, sizes ranging from a small room to just an entire city.

The Olliverse
See also: List of Olliverse Subworlds

The Olliverse has a total of 24 subworlds (18 if counting the Dimensional Dungeons as one), with 13 dimensions (7 if counting the Dimensional Dungeons as one) and 11 realms. Each of these subworlds are divided into three 'planes' - the Transcendental Plane, the Mortal Plane, and the Dark Plane.