Ebay.com is the American website of Ebay. Similarly, cn and hk are China website and Hongkong website respectively. Registered users can use different websites to log in, sell or buy goods. If you apply for an account of any website and pass the verification, you can log on to Ebay websites in other countries, because all Ebay users enjoy the database. In other words, in addition to logging in, you can sell goods at any Ebay website in the world in the default currency of that website.