What is the difference between the formaction and data-send-to properties in yandex turbo rss in a popup form button?

Question

Yandex

I'm trying to set up yandex turbo rss, I need to make a pop-up form button.
Here is the link https://yandex.ru/dev/turbo/doc/rss/elements/fos.html

I can't understand what is the difference between formaction and data-send-to properties? And there and there the mail is indicated