QR stands for Quick Response. If you have a smartphone, iPad2, or tablet computer with a webcam, a QR code is a quick, accurate way to input a web address or phone number using the device's camera - without having to type anything. If you want to provide additional information for your audience, you can't put a clickable hyperlink on a poster, a sheet of paper, or a business card, but you can provide the convenience of a QR code.
Using a QR Code reader on your smartphone, you simply take a picture of the QR code. The reader then redirects you to a web page or some other resource on the internet. Depending on the QR code you find in the library, it could:
Many phones come with QR readers installed. If yours does not have one, search for “QR reader” in your device's app store. Here are some common QR code readers: