This code creates a dropdown list with options for Afghanistan, Albania, Algeria, and many other countries. The "value" attribute of each option corresponds to the ISO 3166-1 alpha-2 country code for that country. The package/library used for creating select_country form elements depends on the framework or CMS being used. However, many PHP frameworks and CMSes provide built-in functions or plugins for creating form elements like select_country. Additionally, there are several third-party libraries such as Symfony Forms and Laravel Collective that provide advanced form features and widgets.