Different Planes of Existence

In one of the theories of existence I've read, it states that aside from
the world we're living in are other planes of existence - different
realities with interwoven connections. Except for rare linking points, each
plane is effectively its own universe with its own natural laws. For
example, there is our plane (the material plane) which coexistent with that
of the Ethereal Plane - a plane which is mirrors that of the Material plane
but exist in a different level. That is, these two planes overlap each
other and yet stuff from one plane cannot affect those on the other. On
many levels, that's how one can describe my existence with Daniel and the
thing that I have to realize.