了解Opencart的加载程序工作流程

I am trying to understand how OpenCart's code works. The following code is defined in index.php (file attached) in OpenCart's mysite.com/admin/ folder. Could you please explain what the following code actually does ? I would like to know how it actually works.

I also have attached loader.php and registry.php under their respective folder.

// Registry
$registry = new Registry();

// Loader
$loader = new Loader($registry);
$registry->set('load', $loader);

link to mysite.com admin folder zip

Though the following question is not similar to my question but still it touches similar point: Opencart meta title include store name

// Registry
$registry = new Registry(); // Loads registry class from /system/engine/registry.php

// Loader
$loader = new Loader($registry); // Loads Loader class from /system/engine/loader.php
$registry->set('load', $loader); // Assigns the class to the registry allowing global use in other classes that use the registry object

Opencart's coding logic is MVC+L (Language) model.

Not for the latest version, but you can learn most of the details about workflow here ; http://www.packtpub.com/article/opencart-layout-structure