QR code (abbreviated from Quick Response Code) is the trademark for a type of matrix barcode (or two-dimensionalbarcode) first designed for the automotive industry in Japan; a barcode is an optically machine-readable label that is attached to an item and that records information related to that item: The information encoded by a QR code may be made up of four standardized types ("modes") of data (numeric, alphanumeric, byte / binary, Kanji) or, through supported extensions, virtually any type of data.

The QR Code system has become popular outside the automotive industry due to its fast readability and greater storage capacity compared to standard UPC barcodes. Applications include product tracking, item identification, time tracking, document management, general marketing, and much more.

A QR code consists of black modules (square dots) arranged in a square grid on a white background, which can be read by an imaging device (such as a camera) and processed using Reed-Solomon error correction until the image can be appropriately interpreted; data is then extracted from patterns present in both horizontal and vertical components of the image.

We use these codes on our website in abundance.  Here you can find some information on smartphone downloads.  Additionally you can learn more about QRcodes at the Wikipedia - Free Encyclopedia website.

I use an Android phone with i-nigma scanner.  It's extremely accurate and fast.