Five quick reminders about consciousness
We understand a lot about consciousness: If by consciousness one is referring to the nature of how humans perceive, experience, and attend to the world, there is a huge amount that has been discovered, as well summarized by authors like Dennett, Dehane, and many others.
We fundamentally don’t understand consciousness: If we look past the details of human experience, we are ultimately confronted with the fact that we have no good explanation for why or how it is possible for there to be anything like “the experience of something” at even the most minimal level, given our current understanding of the nature of the universe, and it’s possible we never will.
Consciousness exists on a spectrum: We experience varying levels of consciousness in ourselves, and it seems reasonable to posit that the same thing holds across different (types of) beings (which we assume are conscious on some level), but there are no obvious places at which to draw hard lines.
There is no test for consciousness: There are any number of reasons why we might theorize something to be conscious, but there is fundamentally no way to test for it.
Consciousness is a process: If nothing else, we can say that consciousness involves an experience of something in time. If we assume that consciousness is some sort of emergent property of information processing (as many do), consciousness cannot exist while information is not being processed.
(see also Consciousness is not strongly emergent by Crispy Chicken)