Transaction: AMAZON

Transaction site Amazon

They make money by providing a place for buyers and sellers to meet.  They make money by selling items that market under their own brand “Amazon Basics”, charging sellers a small fee from them to post their products (this was the norm years ago, not sure if still true), and posting advertisements through out the pages.  Sponsored items get special mention and usually on the top of all searches.

Note: these samples are ones I use, there are millions to choose from and many fall into multiple categories.