eastern esoteric yoga informs us that the human has not only the physical body, but a series of overlapping, multidimensional bodies. these bodies are variously described according to different traditions, but essentially they include the etheric/electromagnetic body (seat of the chakras), the astral/emotional body (the basic formative dimension for emotions as polarized expressions), the mental body (the sphere of abstract knowledge and concrete thinking, the realm of forms). the last is the causal body (seat of the soul, the timeless, spiritualized agent behind sequential human incarnations).
this is pretty self explanatory. the physical body has the lowest vibrations and is attached to the etheric and the astral.
the etheric body can leave the physical, but when it does, i don't think it goes any great distance. i think its role is a "life energy" body. when the body goes to sleep, the etheric expands, the chakras open, and we receive energy and restore our depleted supply. this is why it is also referred to as the vitality sheath or health body. when i'm tired and drained, i can lay down for half an hour, enter a trance like state and wake up feeling totally refreshed. this is not the projection of the astral body, but a charging of the etheric. if the etheric projected a great deal, our bodies would feel drained, not refreshed, upon return. when i astral project, my etheric is doing its job of replenishing my body, and when i come back, i am refreshed. the two are independent.
when people experience "duality" aka mind splitting (where the consciousness resides at two locations) i believe one part of the consciousness is in the etheric and another one is in the astral.
there are also a lot of discrepancies on the silver cord. i personally have never seen this cord (but i haven't really looked for it either). is has been suggested that the cord is related to etheric projection, not astral. if the cord was associated with just astral projection, then we would see it every time we astrally projected.
i remember once leaving my body and out of curiosity i looked back towards my physical body. i saw a body, but it was in a totally different position than my physical! it was the etheric body that i was seeing. in the astral, we see the astral counterparts of the physical, but i think we can also see our etheric shell (this explains why i saw the etheric body, and not the physical).
on several occasions, during meditation, i have been able to see the ceiling through my physical eyelids. this is also not astral projection.
people who are sickly have reported more obes. i think this is because the etheric is weak and the astral is able to separate more easily. both our physical and etheric bodies are magnetic in nature and influence the pull of the astral.
when objects are moved, i think it is more from the influence of the etheric body, rather than the astral which does not share the same vibrations as objects in the physical. the etheric is of a higher vibration than the physical, but lower than the astral.
the astral body is aligned with the physical and is of a lower vibration when it is attached. to unattach, the frequencies must be raised. the astral body can transcend various levels in the astral plane. it reacts to thoughts and can see the astral counterpart of the physical world. it cannot affect physical objects because they do not share the same vibrations. the astral body can transcend time and space. there is a feeling of separation when consciously projecting from the body. rushing, vibrating, roaring, crackling and popping (to name a few). when in the astral, our filter is removed and we are able to see, hear and feel more.
the mental body is where remote viewing happens. when you achieve bi-location during remote viewing, there is no feeling of separation as with astral projection. there is also no visual distortion as there sometimes is with astral projection (depending on where you are at on the astral plane). my first "projection" was a mental one. i went straight from the physical to the mental body which explains why there were no vibrations. i just involuntarily "popped" out and was several blocks away. i also think the mental body is often independent of our physical one. unlike astral projection, when i separate, i detach from the body and travel accordingly. in the mental, you just show up somewhere and have done nothing to travel there. the mental body does not contain the thought "junk" of the astral. you may be able to see partial thoughts formed in the astral (as in a partially built ship), but not in the mental. when i wake up in the mental, i am usually nowhere near my body and have no sensation of a body of any kind. i once "woke up" in the mental and i had no way to determine where i was. it was pitch black, i had no ears, no eyes, no body. it was a void that i remained in until a sudden return to the physical. it was a pure state of 'being'.
the mental body also transcends time and space. advanced remote viewers, using their mental body, communicate telepathically.
the causal body is where past life memories are stored. this plane is one up from the astral. when we die, we enter the astral and eventually experience a second death (the astral body diminishes) and we enter the causal plane where we then remember our past lives and can then make decisions for our next.