picture tag confusion...!

I was looking responsive images playlist, and in last part of that the discussion was all about picture tag and I understand that well. but there is one cunfusion. As shown in the image the source have a media query of (min-width: 960px) and srcset contains three image with 1,2,3 DPR + there intrinsic values. So my question here is that from onward 960px the browser it self find the best image using the PDR value + intrinsic value ? what is the science behind