Augmented reality works a bit like a QR or barcode in that you scan something, but then it gets really fun. While you can simply have the scan take you to a video or web link, you can also overlay a virtual transparency onto the real world. This post from Educational Technology and Mobile Learning features an AR app from Aurasma, but another company Daquri has some pretty fancy stuff as well. One of the cooler AR toys I've seen is the Elements 4D blocks http://elements4d.daqri.com/
http://www.educatorstechnology.com/2015/10/5-ways-to-use-augmented-reality-app.html