A QR code (abbreviated from Quick Response code) is a type of matrix barcode (or two-dimensional code) first designed for the automotive industry. More recently, the system has become popular outside of the industry due to its fast readability and comparatively large storage capacity. The code consists of black modules arranged in a square pattern on a white background. The information encoded can be made up of four standardized kinds ("modes") of data (numeric, alphanumeric, byte/binary, Kanji), or by supported extensions virtually any kind of data - wikipedia.org/wiki/QR_code

Anatomy of a QR code

Audi Japan's QR code advertisement

Adafruit offers QR codes on an iron-on badge and a glossy vinyl sticker as part of our fun and exciting way to celebrate achievement for electronics, science and engineering. We believe everyone should be able to be rewarded for learning a useful skill, a badge is just one of the many ways to show and share. You can also download Adam Kemp's QR skill badge requirements doc at the Adafruit Academy to easily guide your students to earning this badge!