What's the difference between `clipstart` and `playstart`?

When setting up the `content` node on a `video` node, what's the difference between using `clipstart` rather than `playstart`? When would you use one over the other? What does `clipend` do, for that matter?

The Content metadata documentation only says that "ClipStart sets the clip start position of the playback," which isn't very useful. I didn't find anything else about what a "clip" is in this context.

I tried a couple brief tests and couldn't see a difference between using `clipstart` instead of `playstart`. Maybe I'm missing something though.