1) Timeline view is synch'ed with the dopesheet. It's useful to have a timeline near (usually under) the viewport where you manipulate your skeletons, which moving the dopesheet to either side (which puts the dopesheet timeline at the very top of the screen). For example:
Loading Image
2) Current, when active, automatically scrolls the timeline horizontally. This is useful when you are doing a long animation and not all the keys fit in the dopesheet horizontally.
It would be great if you continue to post questions like this, so we can add the missing parts to the docs!
