What is QR code?

QR code (Quick Response Code) is the for a type of matrix barcode first designed for the automotive industry in Japan. Bar codes are optical machine-readable labels attached to items that record information related to the item. Recently, 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. The code consists of black modules (square dots) arranged in a square grid on a white background. The information encoded 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.
A QR code is read by an imaging device, such as a camera, and formatted algorithmically by underlying software 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. As a variety of industries utilize the QR code today, the applications for use can vary from product tracking, item identification, time tracking, document management and general marketing purposes.

There are various online Free Utlities which creates QR code and Decode them
http://goqr.me/
http://www.patrick-wied.at/static/qrgen/
http://www.onlinebarcodereader.com/

These utilities helps to create QR code and encode data into it. Here I have created a QR code which is having a URL for http://www.todaytechtalk.info .

On using any of above utilities you can decode its information.

QR codes now a days is widely used  in Google's Android operating system and iOS devices (iPhone/iPod/iPad). The browser supports URL redirection, which allows QR codes to send metadata to existing applications on the device. mbarcode is a QR code reader for the Maemo operating system. In Apple's iOS, a QR code reader is not natively included, but more than fifty paid and free apps are available with both the ability to scan the codes and hard-link to an external URL.  Goggles is an example of one of many applications that can scan and hard-link URLs for iOS and Android. With BlackBerry devices, the App World application can natively scan QR codes and load any recognized Web URLs on the device's Web browser. Windows Phone 7.5 is able to scan QR codes through the Bing search app.