Front Only
The printer will only print on the front surface of the card, if a two-page document is printed then two separate cards will be produced, one card for each page of the document.
Both Sides
If a 2-page document is printed, the printer will print the first page on the front of the card, flip the card over and print the second page on the back of the card.
Back Only
The printer will only print on the back surface of the card, if a two-page document is printed then two separate cards will be produced, one card for each page of the document.