It's fairly straightforward - "consciousness" is nothing more than a compact way to talk about certain kinds of very complicated interactions of neurons, and those neurons are part of and affect the world. We might not know exactly which neuron firing patterns correspond to "consciousness", but we know that some patterns (say, the one you're experiencing right now) correspond to it, and others (say, a MMA fighter immediately after getting choked to unconciousness) don't.
I don't think this is the LW consensus. This view implies that "consciousness" is a property of neurons, rather than a property of programs or agents. Surely the LW view is that uploads can be conscious.
I also don't think this is straightforward. Where I get confused is when I try to formalize the sense that it's about programs. This implies that there's such a thing as a conscious Turing machine. Is it still conscious if it stops executing? If I implement it on paper?
In Zombies! Zombies? Eliezer mentions that one aspect of consciousness is that it can causally affect the real world, e.g. cause you to say "I feel conscious right now", or result in me typing out these words.
Even if a generally accepted mechanism of consciousness has not been found yet are there any tentative explanations for this "can change world" property? Googling around I was unable to find anything (although Zombies are certainly popular).
I had an idea of how this might work, but just wanted to see if it was worth the effort of writing.