Stain. And lots of it. During the rubbing process, the stain gets up on the spots. Well, if you let it get up there and stay there, the spots will hold the color. If you rub the excess off, you get an antique feel to it. Then when you finish the leather, you apply whatever finish (wax, super shene, saddlelac) over the spots as well, or seal them with a matte finish.