I am sure this have beed asked many time. I even got on few answers but I realy dont get the idea of how to edit any "action" or "filter" hooks in Wordpress + WooCommerce.
As an example on checkout page, at the bottom where is usually the summary of the shopping cart, this info is generated by this code:
<?php do_action( 'woocommerce_thankyou', $order->get_id() ); ?>
I tried different way to search for "woocommerce_thankyou" in other files but I cant find anything. So, how the output code is generated? There must be a file which is called for doing it.