In the following video, Motley Fool tech and telecom analyst Andrew Tonner tells us why he's buying eBay (EBAY 0.17%). Originally centered around the online auction business, it now makes up only about a quarter of the company's sales portfolio. Online auctions is also the company's most stagnant component, compared to its other focuses, pairing with merchants to emulate an Amazon-like (AMZN -0.94%) retail distribution model, and capitalizing on the exploding mobile payments trend with its highly profitable PayPal business. In the video, Andrew gives us some specific numbers for just how big these businesses are for eBay, and how cheap the stock is right now.