examples-3.x-dev/modules/hooks_example/hooks_example.routing.yml

# hooks_example only has one route. It is to a page explaining the module.
hooks_example.description:
  path: '/examples/hooks-example'
  defaults:
    _controller: '\Drupal\hooks_example\Controller\HooksExampleController::description'
    _title: 'Hooks Example'
  requirements:
    _permission: 'access content'