Where are ajax requests sent to bitrix:sale.order.ajax?

Question

1C-Bitrix

Standard bitrix component: sale.order.ajax. When changing the payer type, an ajax request is sent, in response to which a part of the page is returned that is generated in person_type.php, props.php, paysystem.php, delivery.php, related_props.php, summary.php.
In this case, template.php is not called. What file is responsible for processing ajax request?

Answer 1

in init.php create an event handler and change what you want there

Answer 2

There, all form fields are sent to the same address. So the processing goes in component.php. But really not the whole template is loaded, but the files that are included in template.php. What is the task? Do I need to perform any actions when changing the type of payer?