Board Thread:Lore Discussion/@comment-27254145-20151130135311/@comment-26987392-20151201124222

I think this is the easiest way to understand.

The mortal brain cannot comprehend some things very well. It interpretates the Aurbis, the TES universe, as a sort of "solar system".

Nirn is the planet where mortals live, which is made of a few continents, Tamriel being the most important. It's moons are  the interpretation of the splitten soul of Lorkhan. The 8 planes around Nirn are the Eight Divines. Nirn, it's moons and the other planets form what's called Mundus, the mortal realm. Mundus is home to mortals and the Aedra.

Outside Mundus, there is Oblivion. The mortal brain sees Oblivion as the vast, black, nothingness of space. Oblivion is home to Daedra.

Further away, there is Aetherius, the most distant realm(and thus the most difficult to reach). It can't be seen, however, the stars, which are holes the Magna Ge tore into Oblivion after fleeing from the creation of Mundus, can. The strongest of the Magna Ge, Magnus, tore a bigger hole, which is the Sun. Aetherius is home for, well, different entities, including et'Ada and some mortals after their death(i.e. Sovngarde, the nordic afterlife, is a plane of Aetherius).

There is also The Void, which some people say it's the outside of the Aurbis, other say it's the nothingness between realms, others say it is Oblivion itself.