GotGarlic
Chef Extraordinaire
That's a loin alright. A tenderloin is a out 2" in diameter at the thick end and tapers off to a point. It's about a foot long and weighs about 1.0 - 1.5 pounds. It's almost always sold whole and its meat isn't as white as loin meat.
I don't know if this is a regional thing, but a couple of times I bought pork tenderloin and the meat was cut into medallions. I don't remember seeing an indication of this on the package, so it was a surprise