Ah well... we just know. It's just how things are. Anyways if we're talking about definitions. Then I would say, "internals" and "wall" and "external situation" and all that, there are a few definitions for each one so I am not sure what you are looking for here.

What I meant was that mindfulness sometimes is described as paying attention to your mind's stuff, thoughts, feelings going around in your mind, and then sometimes as paying attention to outside, though I'm not sure how that's different from grounding oneself when needed (upset, etc, too high arousal of any kind, mental, emotional).