Ebay has sites all over the globe and is the biggest online auction site in the World. Nothing competes with it.
Set up in 1995 it now has in excess of 50 MILLION registered users and has sales in the BILLIONS of dollars.
Opening an account on Ebay is totally free of charge and allows you to bid, buy and sell on Ebay across the globe to an audience of millions. Because of this fact there are hundreds of thousands of people Worldwide who make their full time living from Ebay alone, some of which make hundreds of thousands of dollars a year and some that even make millions.
It is now such a large avenue that even huge corporations and high street shops sell on Ebay as well as their own websites.