Take looking at a tree. Normally it feels like there's someone here, looking, and a tree out there, being looked at, with a small gap between the two. With non-dual awareness, that gap isn't found. There's just seeing, with "tree" arising as part of that same seeing.
This is often what's happening in the shift of identity that can come with practice, where the usual reference point for self drops from experience. What's left is an unbroken field of awareness, with sights, sounds and sensations simply arising within it. It's just the whole experience, one big non-dual soup, felt in a single arising, moment after moment.
If you'd like to play with this, next time you're looking at something, a tree, a cup, a face, see if you can find the exact line where you end and the seeing begins. No need to force anything. Just look.