K has used so many terms like attention, observation, seeing, awareness etc but conveying about the same meaning, at least to my understanding. And arguably this is the core of his teaching.
So it appears understanding of what he means by this awareness, observation etc. is very essential if one needs get anywhere near to understand the teachings.
I think the term SELF AWARENESS would perfectly capture the essence of what he says. Which means being aware of oneself. And as we identify with our body the most it amounts to being aware of our body and the thoughts within from top to bottom.
So self awareness is being aware of ourselves from top to bottom choicelessly or passively.
Now the main challenge is to be in this state as we live our lives. And that is when things get really interesting.