Switch Terminology
RCM
RCM stands for ReCovery Mode.
Horizon OS (HOS)
Horizon is the name of the Nintendo Switch operating system.
OFW
OFW stands for Original Firmware.
It is your devices unmodified firmware.
CFW
CFW Stands for Custom Firmware.
It is a firmware that modifies the system firmware to allow it to run homebrew.
Homebrew
A term used to describe unofficial software created by developers for a locked down system.
When it comes to the Switch, such software can include save managers, emulators, or games.
Atmosphere
A free and open source CFW created and maintained by SciresM and other contributors.
SXOS
A paid, no longer maintained and closed source CFW created by Team Xecuter.
Does not work with firmware above 11.0.0.
NAND
The NAND is your devices built in memory (not to be confused with the SD card).
The Nintendo Switch has the memory size of 32GB and by default has 25.9GB of free storage, and
the rest is taken up by the operating system.
SysNAND
SysNAND stands for "System NAND".
The SysNAND is the contents stored on your devices built in memory (not to be confused with OFW).
It contains everything ranging from the operating system itself, to games, screenshots, videos, and save files.
Every device, hacked or unhacked, has a SysNAND.
EmuNAND
EmuNAND stands for "Emulated NAND".
The EmuNAND is a copy of your SysNAND that resides on your SD card and not on your devices internal memory.
Think of it as having a secondary Nintendo Switch on your SD card.
It is used to isolate any actions that you might perform from your SysNAND that could either
harm your device or performing any other actions that might get you banned.
Any changes or actions that you perform in your EmuNAND won't affect your SysNAND since it is just a copy.
Having an EmuNAND on its own won't protect you from being banned. Click here for more information on how to avoid being banned.
Signature Patches
Signature patches or SigPatches allow your device to bypass signature checks performed by horizon
for installed titles.
Hekate
A custom bootloader that allows you to bypass fuse checks and has a lot of useful tools.
Can be used to boot into OFW, CFW, Android, Linux, and any other payload.
Fusee
A custom minimal bootloader that is only used to boot into Atmosphere.
The difference between Hekate and Fusee is that Hekate needs a custom configuration file that
tells Atmosphere what KIP's, Patches and other settings it should use, while Fusee boots them automatically.
NSP
Nintendo Submission Package or NSP is either a dump of an installed title or a homebrew package that can be installed.
XCI
NX Card Image or XCI is a dump from a Nintendo Switch cartridge.
NSZ
A compressed NSP file.
XCZ
A compressed XCI file.
NRO
An extension that homebrew applications use.