How does a Genesis child theme understand that the Genesis theme is the parent theme?

Question

In most Genesis child themes, the following line of code exists:

// Starts the engine.
require_once get_template_directory() . '/lib/init.php';

I understand that this includes the init.php file from the lib directory within the Genesis parent theme folder.

My question is simply - why does get_template_directory() return the Genesis parent folder, as opposed to the child theme folder? And how does it identify it if there are multiple parent themes possible?

Answer 1

I'm not experienced with Genesis, specifically, but I imagine its child themes work the same as child themes for any other theme. As documented, a child theme is created by adding a Template: line to the style.css header, which is the directory name of the parent theme:

/*
 Theme Name: Genesis Child Theme
 Template: genesis
*/

By defining the "Template" for a theme, WordPress functions like get_template_directory() know to use that theme's directory for the path or URL.

Answer 2

There is no multiple parent theme possible. Because you specify parent theme by Template: genesis. This helps WordPress to find parent theme.