The "Restore Special Purchases" option allows a new game to restore dresses, bags and other special App Store purchases - items other than in-game currency - to be replaced.  Most users will never have the occasion to use this feature - it's used in the rare instance when a new device is used and the game has been started from the beginning.

 

If you have connected your game via social media, you should be able to log in as you always have, and have all your items and currency intact. See the FAQ entitled "I changed iOS devices. Can I transfer my game from my old device to my new device?"