Running pirated games on the Switch require the usage of external patches. There are two forms of these: ES (Eticket Service) patches and FS (File System) patches. ES patches are for raw/dumped .NSP files that you don't legally own while FS patches are for .NSP files converted from .XCI games or homebrew .NSP files. All CFW have separate patches for ES but certain CFW patch FS via the bootloader (aka the payload) namely ReiNX and Hekate. Atmosphere's ES patches also contain FS patches since their bootloader doesn't support FS patches. If you're not interested in piracy or installing homebrew .NSP files, then these patches are worthless for you. However most CFW bundle the patches such as ReiNX or SDSetup. One CFW that doesn't bundle any patches is Atmosphere and they need to be downloaded separately either from Kosmos or
from a certain thread.
It was released last year on April 24, 2018 when Fusee Gelee was leaked because it was essentially the same exploit as Fusee Gelee but under a different name, shofel2.
Link to the blog post where they revealed the exploit.