A kiss or contour:

Cuts around the sticker but not the liner paper.  If you ordered a circle decal, it would come on a square liner sheet that is easily peeled off for application.

A die-cut

Cuts around the sticker and the liner paper at the same time. This is much like how a cookie cutter (in this example a ‘die’) cuts through the dough.  If you ordered round die-cut decals, you would receive around decal on around liner.