Stupid question, but anyways, the 3DS is incredibly restricted, you can't do anything, so that's where CFW comes in. This allows you to remove those restrictions, sort of like jailbreaking for iOS (unc0ver jailbreak was recently released), or rooting for Android. It makes everything better. You can have custom themes to make your 3DS prettier, install games for free, use emulators to play games, use TWiLight Menu++ to play DS games and make your greatest dreams come true, use cheats, and make a backup of your 3DS in case it gets bricked. That is the only reason why I managed to play literally every single Zelda game possible on the 3DS. Once you finished hacking your 3DS, it makes magic happen. So try it, then maybe you will regret asking this question in the first place. Happy Hacking :3