Cindy, "sandblasting" is where they use a rubber template and "blast", via air pressure, a very fine grade of sand through the "cutout" in the template. The sand will cut into the glass thus creating the "mark". Marble or granite tombstones/headstones for graves are produced via this method.
The "mark" on your wine glass could have been made via "acid etching". Just a "touch" of acid will create the same effect.