The tutorial shows how to make nonuniform or varying IOR (Index of Refraction).
This natural occurring anomaly can be seen in various places; (you will have to research other). Heated glass, rising warm air, different states of ice (pressure related) most commonly you would see it in warped glass found in older homes.
At first it`s usage seems limited, but it can make for very interesting shots. And also the techniques described here can be used to create other complex materials. not relating to Transparency alone.
