In short, a QR (or Quick Response) Code is a type of barcode. If your smartphone has a QR Code Reader application installed you can take a picture of the QR Codes and they will link your phone to a webpage or specific content.
You may find that scanning a QR Code and storing or accessing data directly using your mobile phone is more convenient that writing down URLs or other information on a separate piece of paper.
Most modern mobile phones with a camera will be able to capture QR Codes. However, you may need to install a QR Code Reader application specific to your phone handset before you can read the codes. If not then you can easily install a free one. Download free QR Code reader software.