In short: QR codes are a great way of connecting arbitrary physical items with your smartphone and as a consequence with any kind of web service. A bit similar

In short: QR codes are a great way of connecting arbitrary physical items with your smartphone and as a consequence with any kind of web service. A bit similar to NFC, but with some important differences: they don't require any electronics, work at any range (just make the QR code large enough) and they can be done either by print or displayed on a screen. Additionally, when scanning the QR-code, the user can see the URL it translates to. (Doesn't have to be URLs, but that is probably the most common usage). I am surprised, not more business cards have QR-codes printed on them with the important contact information. But for my personal use, I have a QR-code containing my email address as a picture on my phone, so I can display it for anyone to scan whom I want to give my address to.