What is consciousness?
This is really hard to explain to anyone who isn’t a serious systems geek.
It seems that, as Shar posted, consciousness is awareness of sensations, thoughts, and feelings.
And it seems that it takes many levels of systems to give rise to the sort of consciousness that we as language using human beings experience – about 20 of them. And at each level, there are many classes of very complex processes present.
As someone who spent several years studying biochemistry and neurophysiology, and thirty years running a software business, seeing the sorts of complexity present in those levels of systems is kind of intuitive for me, it all makes sense. Yet trying to explain it to anyone else is almost impossible.
And it seems that our consciousness is a very special sort of software running on top of many other levels of software in a very strange piece of hardware (a human brain).
It seems that all we can actually experience is a software model of reality that the subconscious processes of our brains construct for us – a very slightly (about 1.5th of a second) predictive model of reality. Most of the time we experience what is about to happen, so that we can react in appropriate ways.