The European Article Number (often shortened to EAN) is a standard to encode product numbers. The EAN is a special case of a Global Trade Item Number. The EAN is made of either 8 or 13 digits (EAN-8, and EAN-13). In many cases, the EAN allows to uniquely identify the item. Most of the time, the EAN is printed on the packaging of a product. Special scanners are able to decode these numbers. They then look up the product-specific data (such as the price) and print it on the bill, for exampe.
Note that the EAN is often encoded using a barcode (such as the ones in the example), but this does not have to be thecase. There are other machine-readable codes which can also be used.