HANS is a homebrew app that can enhance the performance of your games, hence the name.
You can do things like:
*Force change the languaje a game runs on (games usually take console languaje by default, in some regions systems don't have several languajes so games never access those in-game launguajes even when developers fully translated their games).
*Adds region free.
*Allows in-game screenshots.
*Can force change the cpu clock rate (N3DS only since it has higher capacity than o3DS, which translates to faster loading times and less frames drops than o3DS would).
*Can read romhacks from the SD card.