Consider two fundamental distinctions:

1. Real vs. Unreal – In the space of all possible worlds, only one is the “real” world; the rest are unreal.  Or if you prefer, among all mathematical structures, only some describe real things; the rest are only abstract math things.

2. Feel vs. Unfeel – Many think they can imagine physical objects just like our brains, except that those brains do not have an associated internal life, i.e., feeling or experience or consciousness.

Once can deny each of these distinctions.  Some claim that all math objects are equally real, or that all possible worlds are just as real.  Others say all physical objects with the right info processes must experience.

While both these concepts seem to me reasonably understandable, it isn’t obvious to me that they are distinct concepts – maybe they are the same concept.  That is, I’m not sure it makes senses to talk about unconscious but real physical brains, or conscious but unreal brains. Maybe what it should mean for a world to be real is that its brains, at least of the right sort, really do feel.

Added:  To clarify, it is not clear it makes sense to posit a real world made of parts which could never be conscious, no matter how they were arranged.  Actually assuming a conducive arrangement is not required.