Same as it works everywhere else: Unless rooted, you can't move the entire app. Because of Android's new security features, no app can be completely moved to the SD Card. The main file will ALWAYS reside in your internal memory. All apps are download to the internal memory. All apps are installed to the internal memory first.
Then, it's up to the dev either to enable moving their app to SD card, to move certain portions (saves, media, etc.), to move only external downloads (extra packages, expansions, etc.), or nothing at all. Again, the main app it's always in your main memory.