This is a really difficult concept for some people in our modern society. Enlightenment style thinking would have you believe that human consciousness is a blanket term for salience, attention, awareness, sentience, social cognition, self-recognition, meta-cognition, etc. It’s as though you looked at a car and didn’t see its component parts or individual qualities, you just saw this weird new thing called Car.

I can tell you from experience, you are not aware of being unconscious. It goes from the moment before you lose it, to when you regain without any period between.