There are many planes and sub-planes of existence on the great Astral Plane of Life—generally known as the Astral World, in order to distinguish it from the Physical World below* it in the vibratory scale. Each plane and sub-plane has its own distinguishing characteristics and phenomena. And yet the same general laws, principles, and characteristic qualities are common to all.
*When we speak of rising from a lower to a higher plane, or of descending from a higher to a lower plane, do not picture an ascent or descent of steps. Nor a rising or descending from one layer of strata to another. Even the familiar symbol of rising from the ocean depths to its surface is incorrect. The nearest mental picture possible to be made of the transition from plane to plane is that of increase or decrease of vibrations as evidenced in sound-waves, light waves, or waves of electricity. By tightening a violin string, one may raise its degree of vibration and, therefore, its note. The same may be done by heating a bar of iron causing its colour to change gradually from a dull red to a delicate violet or white. Or, in the case of a current of electricity, the power may be raised or lowered at will. If a still more material illustration be required, we have the case of the hardest mineral which may be changed into an invisible vapour simply by raising its degree of vibrations by heat. What is true on the lower planes of manifestation is true of the higher. The transition from higher to lower, or lower to higher may be thought of (if desired) as a change of vibration in the energy of which all things are composed.
Life Beyond Death, Yogi Ramacharaka, Yogi Publication Society, Chicago, 1912