What's the difference between 1900 and 2100?

What is the difference between a 1900-2000 and a 2100-2200? This is a question that I see posted on a lot of forums here on chess.com and on sites like Quora. So what is the answer?

At this level, there usually isn't a large tactical difference. Both players will be strong enough not to make egregious blunders. Both probably know a similar amount of opening theory, so there shouldn't be a big difference there.So what is it?

My opinion is that it lies in positional understanding. Knowing typical plans, exploiting ineffective development, knowing good and bad pieces, creating and exploiting weaknesses, etc...

This example game that I played this weekend shows this difference quite clearly. My young opponent is quite strong tactically but lacks a bit positionally. In this game, he botches up his development ever so slightly and then finds himself in a position where he doesn't have the experience to recognize that the pawn break is his only move. Once this opportunity slips, for all intents and purposes I proceed to tighten the screws until he collapses.

I am very proud of this game because this is kind of a game is one that I would not have won a year ago. I have spent a lot of time studying positional squeezes and I finally put one together from start to finish.