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.