Ok ill explain what FS are. *spoiler alert* after you beat the game, there is a city you get access to named Kiloude. There you can find a building named Friend Safari. When you go there turns out it works different than previous generations safaris. Here, for every friend with pokemon x or y that you register in you 3ds a safari space unlocks. How so? well, each has 3 different pokemon in it, and they are divided by types. BUT they get unlocked in YOUR game. Also, you cant see which pokemon the safari has until you enter and search, and the third one is only unlockable after the registered friend for that safari has beaten the Elite Four and both of you must be online at the same time for idk how much time(like 5s maybe?). The pokemon there may have the hidden ability and they have a minimun of 2 perfect IV's.