Hey WikashDebi,
I'm R7anubis, just another user (also an insider), but I'll try my best.
So, there's an option called immersive reader, which is not yet supported on mobile devices ( PC supports it). When you visit certain sites, a book like icon appears at the right end of the search bar of your browser, once you tap on it, it takes you to another page, where it's similar to the reader mode of your Safari browser.
Hope that helps