You have probably followed this link for the ICT Treasure Hunt
What are QR Codes?
A QR Code is a matrix code (or two-dimensional bar code) created by Japanese corporation Denso-Wave in 1994. The "QR" is derived from "Quick Response", as the creator intended the code to allow its contents to be decoded at high speed. (Wikipedia)
For a list of applications which can be installed on phones, go to this link.