This is a nice article about the background of Material Design, as well as how to incorporate into the WordPress UI packages we use at C2IT Consulting. While the end result is simple, it takes some thought to implement the first time around, and this is a great walkthrough of those steps.
Material Design was invented by Google in 2014 in an effort to combine tactile elements (based on the sense of touch) with technological possibilities of the real world and beyond. It capitalizes on the users familiarity with things like paper and ink and adds scientific realities like movement and shadows. It even stretches the real world limitations of technology and science just enough to bend but not break the rules of physics. The result is a design that is both familiar and magical at the same time.S