It all starts with a route, doesn't it? Any interaction with a Drupal 8 website has its beginning in a user (or system) accessing a certain path (or resource). This translates into a route, which maps that resource to a flow that (hopefully) returns a successful response back or at least a graceful failure.
The Drupal 8 routing system is a major shift away from how it was in its previous versions. In Drupal 7 and earlier versions, the routing system was a very Drupal-specific thing (a drupalism, if you will). Many of us remember hook_menu as a staple hook each Drupal developer had to know very well. All of that has been abandoned in Drupal 8 in favor of the Symfony Routing component (http://symfony.com/doc/current/components/routing.html ...
