Windstopper is a thin membrane that's used with other fabrics, like goretex but more breathable and less water resistant.
Something that calls itself Windstopper could be a light shell with the membrane laminated to it, and nothing else (such as one of my gilets, from which the membrane is peeling in large sheets), or it could be a double layer of fairly thick fleece with the membrane in the middle, like the gloves I wore to work this morning.
Windstopper Energy 3 layer is only one of many types of windstopper fabric laminations. It's mainly used in softshell jackets, but it doesn't follow that all windstopper softshell jackets use Windstopper Energy 3 layer fabric (they definitely don't). Going by a quick google, it's used more in workwear than performance outdoor products.