This an example of the post type pages of a Google Sites Blog. The blog post can be viewed as a single page. This Blogging method in Google sites is useful for small updates.
A Bloggers updates can be access through the Google sites feed . Each blog has it's own RSS feed that could be viewed through a Google Gadget and embedding into Google Sites.
JSON has widely replaced RSS and XML, like in Google's Reader project.
Accessing content through JSON produces much faster web performance , especially on mobile or mobile network connections.
Google Apps Script generally uses JSON to parse out the required information directly form Google Sites.
XML feeds are still used by Search engines for website sitemaps etc..