You are referring to a QR code (quick response code). These can be scanned by QR scanners and, more recently, most smartphones. A quick Google search of "make your own QR code" reveals a plethora of free services to create your own custom QR code. The one I recommend is Kaywa http://qrcode.kaywa.com/ which has analytics and performance tracking. These are great resources for businesses and just about anyone else that needs a quick way for targeted traffic to reach your website!