Here's the very dumbed down explanation. SysNAND is the 3DS's internal NAND. It stores the firmware and all important information. The EmuNAND isn't really a NAND at all, but a secondary partition setup on the SD card that you can copy the contents of the 3DS's NAND to. With rxTools and other CFWs, you can have that secondary partition act as the NAND, allowing you to reap the benefits of CFW and newer firmware without having to mess with your SysNAND, so you don't have to worry about bricking it.What is the difference between sysNAND and emuNAND?