What do you mean by "HTML is what gets rendered by the browser"? In the context of using Javascript to modify the DOM. My understanding is that HTML is an inpu

What do you mean by "HTML is what gets rendered by the browser"? In the context of using Javascript to modify the DOM. My understanding is that HTML is an input to the browser, which is translated to the DOM. (Which is then translated to painting the screen, handling inputs etc.) This is an important distinction in context of your point. React (Or any VDOM or similar JS lib) isn't creating HTML; it's creating a set of DOM manipulation instructions in JS.