If you make index.php clonable, then all of it's cloned pages will be mysite.com/page-name.html. In any other case, the template name will show up in the url as if it were a directory:
mysite.com/template-name/page-name.html.

With nested pages the html extension gets dropped as well:
my-site.com/page-name/ or mysite.com/template-name/ or my-site.com/template-name/page-name/

Nested pages goes beyond just what the page names look like, though. You're best off looking at the documentation to decide if nested pages will be useful for you.

yeah think I will have a good read through tomorrow

Thank you so much for the help etc.