A QR Code is a 2 dimensional bar code (see below) that can be scanned & decoded as text by a smart phone. When scanned, the QR code can open a website, load an electronic business card, & more.
To read the code, simply download a barcode reading app from the Appstore. Point your phones camera at the code & the image is registered. To create a QR Code, browse to http://qrcode.kaywa.com/ or another similar site. Once generated, you can download it or just copy & paste it into a document or webpage. QR Codes can be read equally well from a computer screen or printed page.
Below is a QR Code with the URL of the microworx website.
This QR Code contains my contact details like an electronic business card.