How does the browser render the page after receiving HTML, CSS, and JS?

After receiving HTML, CSS, and JS, the browser goes through several stages of page rendering:

1. Parsing HTML — the browser constructs the DOM (Document Object Model), representing the document's structure.
2. Parsing CSS — the CSSOM (CSS Object Model) is built, describing styles.
3. Building the Render Tree — combining DOM and CSSOM into a render tree containing visible elements with their styles.
4. Layout (Reflow) — calculating the exact sizes and positions of elements on the page.
5. Painting — rendering pixels on the screen according to the calculated styles and positions.
6. JS Execution — scripts can modify the DOM and CSSOM, triggering re-layout and repaint stages.

Thus, the browser sequentially constructs the structure, applies styles, calculates layout, and displays the content, updating it as necessary due to JS.