QR* (quick response) codes are two dimensional (2-D) bar codes, similar to the UPC codes found on products in retail stores, but they can hold significantly more data than a regular barcode.
There are many different types of data that can be encoded in a QR code including a website URL, SMS text message, phone number, contact information or even just simple text. The beauty of a QR code is that it can be read by a QR code reader app on a smart phone. When scanned, the app will initiate the encoded action. For example, it will launch the browser and open the requested URL, pre-fill the text message, or load the phone number, so you just have to press a button to complete the action.
QR codes bridge the physical and the digital world, and since anyone with a smart phone can scan a QR code, it is a very useful and versatile marketing tool.