Stripe payment gateway and unoknown button

Stripe payment gateway and unknown button. Why is it used another domain on the landing page when payment checkout is as a landing page?
As I understand Stripe updated their payment landing page.

To better protect your business against card testing fraud, we’re changing how we support payment tokenization with publishable keys. Starting 2025-07-21, publishable key tokenization is only allowed with our prebuilt integrations — Stripe Web Elements, Stripe in-app Elements, and Stripe Checkout.

Thank you for the message!