It's a barcode number used only in the US and nowhere else whatsoever, so of course eBay spams the term "UPC" all over the place. The rest of the world use 13-digit EAN barcodes (or rarely, 8 digits), which is also backwards-compatible with UPCs by adding a zero in front of the UPC number (13-digit EAN and 12-digit UPC barcodes are identical in appearance and are read the same way, except that UPCs lack the first digit, which was grandfathered in as a zero in the EAN format; Australian EANs always start with a 9).