I've been looking around the forums and playing Oblivion and Skyrim, and one thing that is always brought up is that Tamriel is a 'plane of existence'. Now, I could understand that Nirn, or Mundas, is the plane of existence, but the continent of Tamriel? If that's the case, what is Akavir? Or Yokuda? Or Atmora? Are they also planes, or just discarded pallets of creation that the gods' didn't favour?

If Tamriel is a plane of existence, would that mean that crossing to Akavir or the other continents is technically 'plane-hopping?' Are they all planes, too? I would have thought that this would be like going to and from Oblivion via 'rifts' and gates, but just crossing over water...?

Or is this just an oversight where Bethesda tried to tell the audience that the game world is a 'plane', and went with Tamriel instead of Mundas to not confuse anyone?

P.S.

In Oblivion, Mankar Camoran tells the CoC that Tamriel is a plane that should belong to Mehrunes Dagon. Again, why not all of Mundas? Or is this another oversight in Camoran's monologue?