wtf is emummc?

emuMMC is a tool for Nintendo Switch consoles that lets you run the system's internal storage from a SD card instead. In practical terms, this means you can boot and use your Switch from a copy stored on the SD card, leaving the console's built-in storage untouched. This is useful for anyone who wants to experiment with their system, keep backups, or run custom firmware without modifying the original device storage. The tool works by replacing the part of the Switch's software that handles storage devices. It intercepts requests that would normally go to the internal memory and redirects them to files or partitions on your SD card. It supports loading full system images stored as files on the SD card, including backups made with a popular Switch tool called hekate. It can also redirect where the system stores things like game saves and screenshots, and it supports running multiple separate system copies from the same SD card. The main audience is people who modify or customize their Nintendo Switch. For example, if you want to try a different version of the Switch operating system without risking your main setup, you could keep one copy for experimentation and another for everyday use, both on the same SD card. The tool supports Switch system software versions ranging from 1.0.0 through 10.0.0. The project is designed to work alongside two popular Switch customization tools: hekate and Atmosphere. You build it by running a build script, then place the resulting file in a specific folder depending on which of those tools you use. The README does not go into detail on how to set up or configure the tool beyond these build steps, so users would likely need to refer to broader guides for full instructions.