AMD has posted a video to YouTube that explains in fairly simple terms the new features found in its recently released second generation Ryzen processors. Specifically, the video goes over AMD's XFR 2 (eXtreme Frequency Range 2) and Precision Boost 2 technologies.
This is not a deep dive into either technology, but a neat four-and-a-half minute primer on what they do, and how Precision Boost 2 differs from the way it was implemented in the previous generation of Ryzen processors. While neither feature is particularly difficult to grasp, AMD's Robert Hallock does a good job in breaking things down into simple terms, aided by diagrams on a whiteboard.
In short, Ryzen (and other processors) balance temperatures with power and a chip's maximum clockspeed to adjust speeds on the fly for improved performance, and are able to "reward users for having a better cooler." That's XFR2 in a nutshell. Precision Boost 2, meanwhile, affords more flexibility for multiple cores to ramp up in speed as needed
Of course, there's more to it than that. Hallock goes over some of the finer bits in the video below. There's also this blog post by AMD that breaks things down into a little more detail.