QR (Quick Response) barcodes are 2D barcodes invented by Denso Wave. QR bar codes can be scanned by cell phones as well as dedicated barcode scanners. 2D barcodes like QR hold more data than UPC, Code 128, Code 39, or other 1D symbologies.
QR barcodes are suited for double byte languages like Japanese, Chinese, and Korean. They can be formatted to encode URLs, SMS text messages, emails, phone numbers, contact info, calendar events, lat/long, and other data. Phone apps can recognize the various QR barcode types and react accordingly. A URL in a QR barcode would launch the phone's browser, an SMS would launch the messaging application, contact info the address book, etc.
The Denso Wave site has a good overview of QR's unique features. The are several distinct portions in a QR barcode. QR is covered by ISO/IEC 18004:2006
Google's ZXing (Zebra crossing) web site has details about the various types of data that can be included in a QR barcode. Examples of QR in the world are listed elsewhere on this site.
You can make QR barcodes online here on QR-barcodes.com You can make free PNGs or PDFs for only 99ยข.
Don't take my word for it, read this first.
QRdvark for Android devices is available in the Android Market and elsewhere on the net. Search for "QRdvark".
QRdvark uses intents and has an API. Read our dev notes to learn how to use QRdvark within your Android apps.