Can anyone help or point me in the right direction to understand the use of the Compositing Mode and Make Compositing Child buttons on the video tracks?

I've read the small section in the help files multiple times and still don't understand why I would use these buttons instead of what I normally do, which is simply stack layers on top of each other--one on each track, in the order I want them to show through in the final video.

I normally work with green screen, luma key, and even alpha channel video and still clips and obviously, what I've been doing works.

Is there some hidden advantage of these buttons I'm not understanding?

Thanks a lot.