The WordPress REST API makes it easier than ever to use WordPress in new and exciting ways, such as creating Single Page Applications on top of WordPress. You could create a plugin to provide an entirely new admin experiences for WordPress, or create a brand new interactive front-end experience.
The posts you are reading on this site are actually coming from a WordPress application hosted on the Digital Home Canada website. The following screenshot is from the WordPress Backend.
In addition to serving up the posts listed above on this blog page, the movies page is being populated by Movies posts that are also contained within the WordPress back end.
The result is that one WordPress administrative back end can serve up content to multiple websites.