How do Sync Markers work and how to use them?

I understand that you need to put animations into the same Sync Group and put sync markers with the same name in different animations. But I don’t quite understand how it all works and how to properly use this feature. And I can’t for the life of me find any useful information on this. I have read the about Sync Groups but still don’t know how it all really works. Also, how do I blend perfectly between sync markers in two different animations? Help very much appreciated!

It’s basically useless, causes lots of crashing and data corruption, just don’t use it.