This article here seems to believe that the metaverse is nothing but "internet VR". The talk by Carmack for the most part equates the metaverse with MMVR - massively multiuser virtual reality.
But according to the explanation that Raph Koster (the mind behing metaplace - the only prior attempt at ever building a metaverse) recently posted at the Playable Worlds homepage, what Facebook is trying to do, is building a mirror world - which is just one world out of many in a multiverse, which in itself is just one small part of the metaverse...
All that enthusiastic talk about "it's the future!" isn't helping either - if anything that muddies the waters even more.
Right now, we are on the best track of turning "metaverse" into a completely meaningless marketing buzzword. Everyone uses the term, behaving as if it was totally clear and obvious what it meant - but nobody seems to be able to actually produce a clear and to the point explanation or definition.
What actually is the metaverse?