How to connect payment systems correctly, what services?

Question

API

Guys, I welcome everyone. Actually the crux of the matter is this.
I have one product, and I made a page for it. How is payment set up? In which direction to google?
The fact is that if my memory serves me, then there are like services that support many payments at once, and there are api functions that are inserted into the page.
Just bring a little up to date, so to speak, the soil from which to build.
If a service, is the money stored on it? Or is it on the principle of an exchanger? Is IP required for this? Or there are no such troubles. And of course, a link to the current documentation is welcome.
Thank you very much in advance. Have a nice day!

Answer 1

https://kassa.yandex.ru/