chart, page-2

So jxk to the uninitiated amoung us what does this mean?
The converge line which occurs about May 2012 ? Does that mean that those whoever they are who are selling shorts have taken over as the SP then starts to dip dramatically?
What is their rationale ? The theory is that they can then buy enough shares to pay back from those that were borrowed as well accumulate their own. Is that how it works. You can tell I am a new chum(P)