emuMMC (emuNAND): emuMMC is a feature where you can essentially store a second switch on your SD card, complete with fully different games and settings. This serves a few purposes. The most common, in the Switch scene at least, is to use your emuMMC to do things that would normally get you banned but keep the emuMMC offline, and then using your sysMMC (normal system internal memory) without CFW online. The other purpose is to prevent a brick (your system being rendered useless by using software in unintended ways or from malicious programs). These are very uncommon and there’s other ways to fix them as we will describe later, but if you’re very worried then using an emuMMC as extra protection can be a good idea. emuMMC refers to Atmosphere’s specific emuMMC. Note, there are a few things shared between emuMMC and sysMMC. System fuses, and cartridge fuses carry over as well as your console ban state.
sysMMC (sysNAND): sysMMC is the storage in your switch you would use normally. Compared to emuMMC, sysMMC is faster, and stored within your switch. You can use sysMMC only if you wish however in order to safely play online after doing stuff that would risk you getting banned, you either have to restore a clean NAND backup, or go through meme's guide to rebuild and clean up your NAND beforehand. emuMMC on the otherhand is more appealing for this as you have two separate containers instead of just the one.
Fuses: Fuses are a system count of the latest firmware you have been on. Whenever you run your Switch it will check your burned fuse count and the number your firmware is supposed to have. If they don’t match then it will burn fuses to match the firmware’s intended count. This prevents you from going back to older firmware versions, because it will notice that your fuse count is greater than the number it should be. However, Atmosphere CFW will skip the fuse count and will prevent fuse burning so this becomes a non issue when using CFW. In addition, there are fuses for the game cart launcher. These are rarely burned, but when they are you will find that you cannot use game carts until you burn that fuse, even on CFW. Some more info can be found in my guide here.
RCM: RCM stands for ReCovery Mode. The Nintendo Switch uses a Tegra X1 processor, and has a special recovery mode which for the end user isn't useful. Due to how RCM is, and the exploit found with fusee-glee, RCM is the entry way on unpatched Nintendo Switches to booting homebrew/unofficial code.
Clean: Clean is a term used to refer to a NAND that will not be flagged by Nintendo for a ban. While it is a good idea not to use CFW at all on a NAND that you intend to keep clean, it seems that it is likely possible to run homebrew and keep your NAND clean as long as you to not install borrowed games or cheat online. Once you have done anything that will make your NAND dirty the only way to clean it is to restore a NAND backup from when it was clean. Such meme's NAND rebuild guide is a good place to go too, but it's not a guarentee. A factory reset will NOT clean it. The homebrew programs that promise to clean it will likely get your system banned as they leave your logs blank which is not normal and will be noticed by Nintendo and get flagged. If you were offline when getting your system dirty you will be flagged when you go online, regardless of if you’ve deleted the content or not. If you are flagged that means your system will be banned at some unknown time in the future when Nintendo runs a ban wave and bans everyone who has been flagged since the last wave.
XCI and XCZ: An XCI is a dump directly from a retail game cartridge, where an XCZ is a compressed XCI. Usually game leaks will be circulated as an XCI or XCZ as its much easier for a game cartidge to end up out in the wild compared to Nintendo messing something up and having the digital version available before release date.
NSP and NSZ: An NSP is a digital dump from an eShop download, where an NSZ is a compressed NSP. Compared to XCI and XCZs, NSP and NSZs often are smaller in size and more desirable.
fusee-primary vs fss0: Fusee primary is Atmosphere's official payload that is distributed on the github and is the payload you are intended by the Atmosphere devs to boot cfw with. Fss0 is a method commonly associated with Kosmos that involves Hekate loading into Atmosphere directly without fusee-primary. Fss0 will ignore many of Atmosphere's settings options, using Hekate's instead as well as requiring Hekate specific fs sigpatches instead of using the normal format.
"My switch cant enter rcm so it is bricked" RCM has nothing to do with your switch being bricked, a bricked unit can still enter RCM. If you truly cant enter RCM your hardware is broken, but more likely the battery is dead or you are in RCM and dont know it.
Misusing the terms emunand, sysnand, ofw and cfw: Emunand and sysnand are not synonyms for cfw and ofw. Emunand and sysnand refer specifically to where you are loading your system from. With emunand you load the system firmware from your sd card, while sysnand loads it from the internel nand in the console. Cfw and ofw refers to if you are loading a cfw like atmosphere, sxos or reinx, or if you are loading the normal system firmware unpatched. You CAN run both cfw or ofw on sysnand and you can run both cfw or ofw on emunand.
When someone says they are updating their cfw, it refers specifically to the cfw files on their sd card, not to updating the firmware of the nand they use cfw on. Similarly updating ofw refers to updating the system firmware version (not cfw) but does not specify sysnand or emunand.
Short answer, no.
Long answer, no. exFAT since the Switch launched has been problematic due to how Nintendo implemented it. exFAT only has one file table where FAT32 has two tables. This is important to know because when exFAT encounters an error, its much more likely to write garbage to your SD card where FAT32 having two tables is much less likely. exFAT is more likely to corrupt/have issues on Switches with Homebrew compared to FAT32, but that doesn't mean there hasn't been issues with non-homebrewd Switches having issues with exFAT.
If you were wanting to use exFAT to install games over 4GB, you can always install them over USB via Tinfoil and NUT, or MTP for example. The Switch never stores any files over 4GB on the SD card, even if its formatted as exFAT.
Goldleaf is a homebrew application that has a few functions, such as changing your user profile image on your switch, viewing installed title information, clearing system updates, and installing NSPs. You shouldn't use Goldleaf to install games as it lacks something called NCA checks. Awoo-installer, Tinleaf, and Tinfoil for example all have NCA checks which are desirable.
You can look at NCA checks like a digital signature to a file. If the file is modified, those checks would then fail. Homebrew applications which utilize these checks for example are Awoo-installer, Tinleaf, and Tinfoil. If you were to try and install a game that was modified, these installers would warn you about this and possibly prevent you from installing that game. This is desirable because you don't know if the file was a bad convert, or something malicious that could attempt to brick your console. Goldleaf does not have these checks, and is not recommended to be used for installing NSPs.
What is 90DNS?
90DNS is a Nintendo Switch DNS which exists to block all of Nintendo's servers. Features 90DNS blocks are the eShop, firmware, and game updates, telementry, social feature and online play. This is desirable because then if you do anything deemed dirty such as game borrowing, using Tinfoil, won't get sent up to Nintendo to flag and ban your console.
What is Incognito?
Incognito's end goal is similar 90DNS, however its something either applied by Atmosphere, or written to your NAND either built into the Nintendo Switch, or an emuMMC setup that is on your SD card. Incognito has the advantage of being something you don't have to remember to set up whenever you connect to a new network connection, and unlike 90DNS, which often slows down your download speeds when using Awoo-installer, or Tinfoil. Incognito doesn't affect them due to the natures of how it works.
Thanks Ibcap for a large chunk of info for this page and getting me to make it.