Originally, if you wanted to know the price of something (or any information about a product), you would talk to the kindly old shopkeeper behind the counter. Then, as things got more impersonal, we developed the barcode: that series of thick 'n' thin lines that could be scanned by computer.
The next stage of development was the QR code. It's like a leveled-up bar code. A square (or matrix, if you want to be fancy) consisting of a collage of black and white blocks. They work like bar codes, in that, with the proper reader (often tied to a smartphone), they bring up information about the item marked with the code.
