Re what is Fey.
The ethereal plane is the same thing as the spirit world. The part of it that is energized by positivity is the feywild. The part of it that is dampened by negativity is the shadowfell.
Ghosts gravitate to the shadowfell because it is easier to rest there. Ghosts are an aspect of an individuals consciounsciousness, but not necessarily all of it. Much of the consciousness might be in the astral plane or reincarnating thru the material plane.
The ethereal plane is a broad spectrum from positive to negative frequencies. In the mid range, is the shallow ether, and is a mix of fey, shadow (like ghosts), and neutral frequencies.
The deep ether includes the feywild and the shadowfell, but also includes the neutral deep ether, the elemental ether, whose borders are between the shallow ether and the elemental planes of earth, water, air, and fire.
The shallow ether is the part that is actually inside the material plane. The elements in the material plane are the states of matter: earth (solid), water (liquid), air (gas), and fire (plasma). The plasma relates to the sun, stars, lightning, and similar, and is sometimes called the heavenly fire. The fifth element is ether, namely force.
Force is mysterious because where the other elements are states of matter, force has no matter but is physical. Natural forces like gravity and magnetism are made out of ether. But also the mysterious forces of souls, such as telekinesis and the vitual bodies of ghosts and fey and outofbody projections of living humans are all made out of ether.
All of the ethereal forces that are part of the material plane and that interact with the objects of matter, are together referred to as the "shallow ether". The deep ether is the rest of the ethereal plane that is beyond the material plane. The deep ether includes the fey, the shadow, and the elemental ether.
Note, that the elemental planes of fire, air water, and earth are immaterial, and are far away from the material plane. Rather, these planes are the "forms" of matter, but not matter itself. They are the plans, that the thoughts of the astral plane construct out of ether, to be the building blocks that will shape the forms of matter in the material plane. The elemental chaos is the border between the elemental forms and the intellects of astral plane.
The aster is the stuff of pure thought without matter or force. The astral realm is a dreamscape of symbols, archetypes, paradigms, logic and emotion. Astral objects are near or far from each other depending on how similar or different they are from each other, and how strong the associations and connotations are between them.
In sum, the astral plane is the realm of thoughts, the ethereal plane is the realm of forces and spirits, including positive fey and negative shadow, and the material plane is this world of physicality as we know it.