What is it not? It's nothing and it's everything.

Clever one-liners aside, I don't think that there is a way to unambiguously define consciousness in positive terms. Even a term such as consciousness is misleading. There is no way to point a finger and say, “This thing here is consciousness.” (Well, TBH there is, but you either end up with consciousness as phenomenon or consciousness as illusion, and neither of those outcomes is true.)

Many people in history tried to define consciousness, but all ultimately failed. The very nature of language and consciousness prevent it. After all, a subsystem cannot adequately express the overarching whole, especially, if the whole is insubstantial, formless, not limited, and so on, yet is all there is, and it's you.

So to answer your question – it's neither this, nor that.