There has been a lot of blog posts how to use the new hook_menu/page callback equivalent in Drupal 8 (http://effulgentsia.drupalgardens.com/content/drupal-8-hello-oop-hello-w... for a great reference) on that.

On the other hand these posts don't cover how the routing system actually works, so here comes a series of posts, how the routing system works in Drupal 8.

The basic part.

The really basic idea behind the symfony control flow is the following:

• A HTTP Request comes in.
• The Request is converted into a response.
• The Response is send.

That's so much for the first post but there will be more over the time.
Please ask questions so we can figure out how to put that into a proper piece of documentation.