Yep, we'll have a video that explains it available in a day or two!
For now, briefly, it lets you set breakdown keys that are more like the previous or next keys. This is useful when using a pose-to-pose workflow: create your main poses, then use the favor tool between them to create breakdown poses. After that there should be only a little bit of work remaining to polish the animation. The favor tool can make animating very fast.
