A: emuMMC stands for emulated MMC (or NAND), you can look at this as having a second operating system for your switch on your SD card. This is appealing because you can then do things deemed dirty on your emuMMC, such as using Tinfoil, installing games from shops, or cheating in games without dirtying your sysMMC. Then you can use your sysMMC for normal Nintendo Online stuff.
Step 2. Take the SD card out of your switch and plug it into your computer.
Step 3. Open hekate_ctcaer_X.X.X_Nyx_X.X.X.zip, extract bootloader to your SD card, and hekate_ctcaer_X.X.X.bin to your desktop (Where X.X.X is the release version).
Step 4. Inject hekate_ctcaer_X.X.X as the payload to your switch (This will be used to partition your SD card).
Step 5. Select Tools by tapping on it.
Step 7. Select Archive bit * AutoRCM * Touch Tuning by tapping on it.
Step 8. SelectPartition SD Card by tapping on it.
Hekate will give you a popup after it checks if it can back up the files on your SD card. If you have more than 1GB of files, and Hekate warns you saying Your SD Card cannot be backed up! follow the guide using the link below.