The United States Congress debates and passes laws; institutions set up to make sure laws are followed are regulatory agencies. The agency regulating medicines, medical devices, vaccines, biologics is the Food and Drug Administration, the FDA.
The front page of the FDA website, www.fda.gov, looks beautiful, and logical. Every link works. The problem is that the front page is updated regularly and you will not be able to link to many documents that are stored on their servers. When you find a document from a search engine, or by happening to open it, save it. You may never find it again. The FDA has probably one, or 10, million pages on its site. Maybe more. Who knows? Probably not even them.
The FDA produces videos explaining what it does in general, and specifically. Simply, it takes the laws, from the Federal Register.