Lenses vs. Screensets

So, I was playing around with Lenses the other day, and perhaps I had one expectation that would have made a lot of sense to me, but the more I monkeyed with it, the more Screensets made sense.

When I think of a lens, I think of something like a sniper's scope, depending on how wide-angle or telescoping the lens is. The first concept that popped into my mind was a swift way to bring up a floating Mix Console while in the Track-View screenset, make an adjustment, and then make it go away.

Is there a video describing more of what lenses is all about? I must be missing the point, and how this would be more useful than screensets.