“ÆTHER, in esotericism, is the very quintessence of all possible energy, and it is certainly to this universal agent (composed of many agents) that all the manifestations of energy in the material, psychic and spiritual worlds are due.” -Helena Petrovna Blavatsky - The Secret Doctrine
Æthereal comes from Latin aether "the upper pure, bright air; sky, firmament," from Greek aither "upper air; bright, purer air; the sky" (opposed to aer "the lower air"), from aithein "to burn, shine," from aidh - "to burn."
The Ether is the condensation of a substance called Akasha(undifferentiated primordial matter).
"Astronomers have discovered, with their powerful telescopes, worlds in a protoplasmic state. These protoplasmic worlds have come out from within the Ether. We can accept, by simple logical induction, that Ethereal worlds exist. Maybe some scientists will not be pleased with the term “Ethereal.” However, the term is of the least importance. The importance is the fact. Every world, before becoming protoplasmic, exists in an Ethereal state. The great Hindustani scientist Rama Prasad stated: “Everything comes out from within the Ether. Everything returns into the Ether.” If protoplasm emerges from within the Ether, then we have to accept that the Ether is in the vital depth of everything that exists." -Samael Aun Weor - Fundamental Notions of Endocrinology and Criminology
"This highest Logoic centre of the cosmos is the primordial source from which all differentiated beings come into existence and to which they return. It is all in all, and the binding force of all. In it the many live, move and have their being. It is the law of growth and the entelechy of all existence. All the manifested processes of cosmic life, with their complex interplay of creation, continuity and change, are crystalline aspects of the meta-biological Logoic life within and beyond the cosmos. As that universal current of life is itself unborn and self-existent, there is that in its reflected modes which cannot be construed in terms of any finite sequence of antecedents or formal set of preconditions." -Quoted from MagusFionn
All of physical life within the third dimension is sustained by the vital / ethereal processes within the fourth dimension. In our body, these are delicately balanced in four interpenetrating "ethers."
The Ether exists in an igneous state (Tejas), in a gaseous fluidic state as the origin of air (Vayu), in an aqueous state as the origin of water (Apas), and in a petreous state as the origin of minerals (Prithvi).
The vital body controls the whole motor vessel nervous system and is the very seat of life itself.