It's basically a very powerful in-game screenshot capture program that lets you take pictures from practically anywhere (not just over Geralt's shoulders). If you have one of these supported cards you should be able to access it during the game (though not during cutscenes).
For future reference, you don't need to put the leader of a country as the ruler of each location. It's put as owner/ruler to fit all possible locations (like palaces are generally ruled over but not a hut). For example, Crow's Perch is put down as the Bloody Baron though it's actually ruled over by Temeria.