How do aggregators, such as skyscanner, or Yandex-Avia, work?

Question

Payment systems

Interested in what are the conditions for the work of aggregators of goods?
How do they have information about prices and availability of goods on seller sites. Do I need to contact the seller? Or can the aggregator be forced to parse the seller's website and thereby update its information? How is payment made if the buyer makes it on the aggregator site? What is the most reliable organization scheme for the aggregator (parsing or docking with the technical support of seller sites so that there is up-to-date information in real time between the aggregator site and the seller site?
Everything looks chaotic here, but I think there will be more questions in the course of the conversation. Please be more tolerant if they seem lamer to you.

Answer 1

Companies like Yandex do not parse anything, but offer their own API for interacting with stores. Parsing sites is too expensive and unreliable, but pushing your API with your reputation is very good.
+ If you want to make a payment, then you can’t do without such interaction at all.