An online auction site is a website where users can buy and sell items through an online bidding process. eBay is one of the most popular online auction sites, with millions of users around the world. It was founded in 1995 and has since become one of the largest e-commerce websites in the world. eBay allows users to list items for sale, set a starting price, and then let buyers bid on the item until the listing ends. The highest bidder at the end of the auction wins the item.