A QR code can be scanned and read by a specifically designed reader device or any type of imaging device with proper software support. Nowadays, all smart phone devices have QR code reading applications to read the QR codes.
QR codes have so many application areas, endless opportunities to discover.
Here is a way that I use QR codes to enable the audience to see the presentations on their mobile devices: http://youtu.be/GFkAyFE3igQ
Vedat YOZKAT