a popular image associated with bitcoin is a qr code. qr codes are a group of black and white boxes that are similar to barcodes. barcodes are a row of lines, and qr codes are a grid of squares. bitcoin uses qr codes because they can store more information in a small space, and a camera such as a smartphone can read them. the two qr codes on the bitcoin note are the public and private addresses, and can be scanned with a number of online tools.