There are many views of reality, but many enlightened mortals believe the Daedric view of reality as the truth.
The Three Planes[]
To the Daedra, Reality is simply divided into three Planes: Oblivion, Mundus, and The Void.
Mundus is what most mortals believe is all of existence. To higher beings, it is where the realms of the living reside (though there are some afterlifes in Mundus). The realms of Mundus are populated majorly by mortals and other lesser beings. Daedra and Aedra both have limited influence in Mundus, but what influence they have is deeply rooted.
Oblivion is home to the Daedra and Aedra. It is also home to most afterlifes, gods, and other lesser entities of "immortal" status. Here the Aedra and Daedra are supreme, however space is limited. Unlike Mundus where there are realms that split apart constantly so as all choices can exist, the Realms of Oblivion do not. If a new realm is to exist in Oblivion, if must be requested from the Void or stolen from Mundus.
The Void is what Mundus and Oblivion occupy. No being in either Mundus or Oblivion hold sway here. It is mastered by Sithis alone. The Void is in a state of Chaos beyond even the Aedra's and Daedra's understanding, even though they were born from it.
Speical Realms[]
There are three realms noteworthy enough to be mentioned; Splinter Realms, Dead Realms, and Outer Realms.
Splinter Realms are a natural phenomenon. They are realms that reside in both Mundus and Oblivion. They usually are unvisitable as they tend to have no form, they instead act like links between realms or are merely places of pure energy one can draw upon. They are more commonplace and more connected to realms of Mundus that lie close to Oblivion. (e.g: Basically any "planes" where a player's character draws energy from. Mana Plane, Ethereal Planes, and so forth)
Dead Realms are entirely artificial and usually are sustained by beings within it, though the power they use to do so may not. A Dead Realm is a realm of Mundus that should have died and fallen into the Void. This nature lends a greater chaotic nature to the realm, allowing simple mortals power beyond mortals in the rest of Mundus can achieve due to the fact the "laws of reality" are dying in this realm. Dead Realms are highly parasitic to either it's own inhabitants and/or any realms it can access. (e.g. Madoka Magica would be a prime example of a Dead Realm. Kyubey's use of Grief Seeds to hold off Entropy. The greater beings in this realm have turned to harvesting emotional energy to hold off the realm's destruction since their own universe no longer has any natural energy to support itself with.)
Outer Realms are similar to Dead Realms. They are realms in Oblivion that threaten to fall into the void. However the outer realms are not under any threat of running out of energy, just the concept of existing. It is here that even Aedra and Daedra will be at thier weakest due to the True Chaos that infests these realms. Very few of them exist, some are natural and came from the Void. Others are not, though how an outer realm could be artifical is not within a mortal's ability to understand.