are alternate dimensions; a places which can't be reached by traveling in any direction through our normal three-dimensional universe. Most commonly, different planes have changes in their laws of nature (often reflected through development ratings) which means that things which are common on one plane (or in our own universe) may be unusual or impossible in another, or vice versa. See Also: The Continuum, Realm
There are 7 Planes or Dimensions of Existence: Physical, Astral, Causal, Akashic, Mental, Messianic, and Buddhaic. The Physical Plane is the densest plane, while the Buddhaic Plane is the least dense. The Buddhaic Plane encompasses all Planes, and each Plane encompasses the denser Planes within it, much like spheres within spheres of existence. The less dense a Plane, the more it permeates the denser Planes, so, for example, the Causal Plane permeates the Astral and Physical, while the Physical does not extend beyond itself (being the densest). All souls will experience life beyond the Physical Plane on each of these Planes as a means of progressive return to Tao.