I’d start with the basics of digital preservation and then move into the technical terminology. Understanding what an emulator does is useful before worrying about individual file formats. After that, concepts such as cartridge images, installable packages, updates and compatibility become easier to understand. You’ll probably encounter phrases such as Get your favourite Nintendo Switch ROM while researching the subject, but it’s important to distinguish casual terminology from the technical meaning of the files being discussed. Preservation should ideally involve software that you have the legal right to back up. Once you understand that distinction, you can explore how NSP and XCI are structured and how different emulators interact with them.