Rendering flow

The Magento application entry point is its index.php file. All of the HTTP requests go through it.

Let's analyze the (trimmed) version of the index.php file as follows:

//PART-1-1
require __DIR__ . '/app/bootstrap.php';

//PART-1-2
$bootstrap = \Magento\Framework\App\Bootstrap::create(BP, $_SERVER);

//PART-1-3
$app = $bootstrap-> createApplication('Magento\Framework\App\Http');

//PART-1-4
$bootstrap->run($app);

PART-1-1 of the preceding code simply includes /app/bootstrap.php into the code. What happens inside the bootstrap is the inclusion of app/autoload.php and app/functions.php. The functions file contains a single __() function, used for translation purposes, returning an instance of the \Magento\Framework\Phrase object. Without going into the details of the auto-load file, it is suffice to say it handles the auto-loading of all our class files across Magento.

PART-1-2 is simply a static create method call to obtain the instance of the \Magento\Framework\App\Bootstrap...