Printed on archival Moab or Canson Rag Photographique paper.
Depending on the size, it will be shipped flat and relaxed in an envelope or rolled in a sleek tube which can be gifted as a rainstick (add uncooked rice). 
Also, depending on the dimensions you order, there will be about a 1-inch, white border around the image. In some cases, when the original painting's dimensions are rectangular and not an exact fit with the size you'd like, there will be slightly more of a border on the sides or top/bottom. But don't worry, a little extra breathing room is always a good move.