You can earn from its partner network as a publisher or affiliate of eBay. For more information, go to ebaypartnernetwork.com/files/hub/en-US/index.html and do the following task: i) Register ii) Advertise the eBay products iii) Getting paid iv) Optimize your site
eBay is a world's online market place for buyers and sellers. They come together and trade almost everything.
ebay is a huge shop site that you can buy (also sell) everything (at least the almost) in it. I wonder if ebay is the first site on this job...