A photographer friend sent a circle of friends saying that his photos were purchased and used by a large advertisement. How do they sell photos?

Part of it is commissioned shooting, and public relations companies or advertising companies find these photographers to pay for shooting; There is also a kind of purchase through the photo library. After the photographer signed a contract with China Luohai Station Cool, he uploaded his photos to the photo library and sold them by Luohai. After the advertising company pays for the use of pictures, the photo library is divided into photographers. Interested parties can sign up for a try. Maybe one day your photo will appear in some big-name advertisements.