It is an ink based transfer printed onto special paper (obviously with sublimation Ink). It is then transferred onto the "medium" ie special coated mugs, license plates and a ton of other items including polyester clothing using a heat press.Kudos to your wife.
Can you explain sublimation printing to us dummies?
The heat activates the the ink to migrate to the receiving surface with incredible color and detail.
If you have seen modern soccer jerseys or those bicyclists passing you with vibrant shirts, those are done sublimation.