Right, in the most simple situation, delivering simple HTML pages, it works something like this:
Browser: Can I have this file (index.html)?
Server: Ah, it's an HTML file, yes, here you are...
Fine, works well, but a little bit boring for the server. But then, what does it care? It's a machine.
Right, now for another jolly picture, before it all gets too complicated...
(to be continued)