I didn't find any clear answer to this issue unfortunately so anyone with a clear explanation answer much more be appreciated!

Amazon seems to be a multipage web application bc every button and every section you click is reloading the whole page(refreshes the page and shows another page opposite to single web application which is instant and one page without reloading)

So despite which Amazon has millions of pages and each page will refresh when you click to, so they have separate html files( .HTMl) for each page or something different is here?