In Vedantic & Yogic thought the energy body refers to the second kosha,layer or sheath, pranamayakosha, right after the physical body. Then you get subtler and progressively subtler conceptions.The metaphor of an onion is often used,a series of layers,5 koshas, encased within a whole.See here:-
http://www.swamij.com/koshas.htmNow my understanding is that,'Etheric body' and 'astral body' are terms(not Sanskrit) that are variously used & pulled or re-appropriated from other traditions(non-clasical yoga and Other).I had to look that up but there was some reference to the Western (Neo-)Theosophical tradition ,and an attempt to blend with eastern esotericism.
You will actually find a remarkable variety of schemas,though with much similarities,and convergence, if you look here:-
http://en.wikipedia.org/wiki/Plane_(esotericism)These are planes of existence, states of Conciousness or subtle bodies beyond, transcending the physical body.So you go from the gross to subtler and subtler- outwards to inwards. You've even got Surat Shabda Yoga in that wiki 'Planes' link- i remember someone (or two) mentioning they practiced that here.
The Causal body is significant- i've imagined it as the karmic body but it's regarded as the subtlest conception, the seed of future incarnations.
Within the context of AYP practices SbP works on the Prana-maya-kosha(energy-veil-sheath,the sheath containing energy) the second kosha. And DM works on the next sheath, Manamayakosha( the Mind sheath), and actually beyond.It's just that we use the Mind(in the form of the mantra) to go beyond Mind through the mantra vehicle to penetrate into subtler sheaths, states of Conciousnes ,wisdom sheath all the way to the Bliss Sheath,AnandaMayaKosha( that veil penetratiing our Blissful nature), or Pure Bliss Consciousness. This is sometimes also called the Fourth state(waking,dreaming & dreamless sleep being the other 3),
Tuirya, Ultimate Reality and undifferentiated boundless Consciousness( where object and subject dissolve and the witness is watching. You can read more here:-
http://en.wikipedia.org/wiki/TuriyaThe innermost is like the Atman or Self(soul) within a classical 5 koshas ( sheaths) schema.
If you do DM, close you eyes etc,you'll notice all these concepts/divisions/mathematical ordering dissolve anyway.
Hope this explains things somewhat.
You are obviously gifted with an inquisitve and questioning( very good thing!) intelligent Mind.
Another thing is that the energy body is Prana,Life Force, carried through the breath (though i suspect you knew that one) It's made up of nadis- the main ones sushumna(where Kundalini rises),ida and pingala(lesser two,left right etc)