How do payment systems now inform the seller about the fact of payment?

Question

Payment systems

I found a document: www.maxbabich.ru/media/paysystem.pdf Нн
2009.
It says that payment systems are divided into only two types according to the methods of notifying the seller site about accepting money in his favor.
The first type of payment systems independently informs the seller about the fact of payment.
According to the second type, you yourself need to pull the payment system using the API.
How do payment systems now inform the seller about the fact of payment?
Is it necessary to write code of the second type, which will pull the payment system itself?
At the moment I'm attaching the project to 2checkout, where the system itself notifies you.

Answer 1

Read the API documentation of your system, but usually the result of the operation is given to a specific url so that you can know whether the payment was successful or not.