A QR code (quick response code) is a two dimensional bar code that consists of black squares arranged in a grid on a white background.
They are very similar to bar codes but are two dimensional and can contain much more information.
They can be read by a QR scanner or reader and contain information like production information,web addresses, email,device setup information etc.
On Android phones and tablets you need a device equipped with a camera and a QR Reader App.
Getting a QR Reader or Scanner
Because of the growing use of QR codes A QR Code reader APP is one of the must have APPs on your Android phone or tablet.
To get an APP just go to the play store and search for QR reader:
You may want to download a few and see which one you prefer as some are much easier to use than others.
Creating QR codes
There are many online websites that let you create QR codes for free.
The QR code on this page was created using qrcode-monkey.com website.
The size the QR code needs to be depends on the distance between the QR code and the camera doing the scanning. A QR code appearing in a magazine can can scanned from a short range and so can be small. See this article for more details
Using QR codes
This video shows you how to use QR codes and explains some possible uses: