What are QR Codes?
Basically, a QR Code is a barcode on steroids. QR codes can be embedded with a number of things, a URL, data or text, or even a phone number, and are typically used to enhance paper marketing with rich media or further information.
How can I use them?
There are a number of apps in the iPhone App Store that can read QR Codes, including the free QR Reader. Most Android phones and BlackBerries are able to read the codes right out of the box, as can newer Nokia handsets. All you need to do is launch the appropriate app, and point your phone's camera at the QR code you want to scan.