How do travel agency websites work?

Question

API

Good afternoon
There are many sites of travel agencies, many have the ability to search for a tour.
Where do they get up-to-date information about tours?
Is the search based on one tour operator or several?
Is there an API for tour operators?
Can, who faced with the development of such a site.
Thank you.

Answer 1

All tour operators sell this data for money, either just a widget or just access to the database like api.

Answer 2

API in almost 99 percent of cases.

Answer 3

I ADVISE: THE ELECTRONIC SYSTEM OF THE TOURISM AUTHORIZATION AGENCY TO PROMOTE AND PROCESS INFORMATION AND OBTAIN A VISA, I will leave a link here, all information is relevant https://estavisa.com.au