Have you even skimmed through The Kybalion yet…?
"At the beginning we may as well consider the question so often asked by the neophyte, who desires to be informed regarding the meaning of the word “Plane,” which term has been very freely used, and very poorly explained, in many recent works upon the subject of occultism. The question is generally about as fellows: “Is a Plane a place having dimensions, or is it merely a condition or state?” We answer: “No, not a place, nor ordinary dimension of space; and yet more than a state or condition. it may be considered as a state or condition, and yet the state or condition is a degree of dimension, in a scale subject to measurement.” Somewhat paradoxical, is it not? But let us examine the matter. A “dimension,” you know, is “a measure in a straight line, relating to measure,” etc. The ordinary dimensions of space are length, breadth, and height, or perhaps length, breadth, height, thickness or
circumference. But there is another dimension of “created things,” or “measure in a straight line,” known to occultists, and to scientists as well, although the latter have not as yet applied the term “dimension” to it–and this new dimension, which, by the way, is the much speculated about ““Fourth Dimension,” is the standard used in determining the degrees or “planes.”
This Fourth Dimension may be called “the Dimension of Vibration.” It is a fact well known to modern science, as well as to the Hermetists who have embodied the truth in their “Third Hermetic Principle,” that “everything is in motion; everything vibrates; nothing is at rest.”From the highest manifestation, to the lowest, everything and all things Vibrate. Not only do they vibrate at different rates of motion, but as in different directions and in a different manner. The degrees of the “rate” of vibrations constitute the degrees of measurement on the Scale of Vibrations–in other words the degrees of the Fourth Dimension. And these degrees form what occultists call “Planes.” The higher the degree of rate of vibration, the higher the plane, and the higher the manifestation of Life occupying that plane. So that while a plane is not “a place,” nor yet “a state or condition,” yet it possesses qualities common to both. We shall have more to say regarding the subject of the scale of Vibrations in our next lessons, in which we shall consider the Hermetic Principle of Vibration."
- The Kybalion, Chapter VIII - The Planes of Correspondence