I’ve seen these around, they are used to tag inventory, or to encode a web site address in posters, etc. Most phones have an app you can decode them with.
2D barcodes can contain more information than your regular 1D barcodes. There are many different varieties floating around, the most ubiquitous being the QR Code. It was created in Japan in 1994, and although Denso Wave holds a patent on them, they have chosen not to exercise it.