Prior to the Moonrise Event only a single plane of existence, the physical world in which people exist, was known. In the aftermath of the Moonrise Event, it has become apparent that there are two, a physical plane and a spiritual plane.
The Physical Plane is the world people usually inhabit, and in which they go about their everyday lives. Everything in this plane tends to follow well-defined and understood rules that remain consistent.
An abstract space akin to a dream. An area of the Spiritual Plane will generally be self-consistent in terms of the rules it follows, but these are not necessarily immediately obvious or traditionally logical. Anything could happen on the Spiritual Plane.
By visiting the Spiritual Plane and fulfilling some requirement there, an act known as a Vision Quest, further power and insight into one's own nature can be gained. It is recognised that the mysterious new abilities wielded by the Enlightened are in some way connected with this plane, as only by embarking on Vision Quests can these abilities be recharged or developed.
There are points around the world where for whatever reason there seem to be ways to pass between the Physical and Spiritual planes and embark on a Vision Quest. Spirit Guides can also develop the ability to manipulate the boundary between these planes in various ways, including pulling their allies between the two planes at will.
Sometimes people find themselves dreaming about a space similar to the Spiritual Plane, in which they have various tasks they feel an urge to fulfil. Since this seems to happen over a wider area of the Spiritual Plane and last for longer, this is known as a Greater Vision Quest.