Simply put, Citrahold provides you with everything you need to easily move game saves from a physical 3DS to a 3DS emulator on your computer (and vice versa).
This sounds like a niche issue, but this solves a major issue for me. I quite enjoy emulating Pokemon at high resolutions, but I still want to play it on the train.
I would like to keep my saves though, and be able to move them back and forth. Kind of like a poor man's Switch (as someone else has put it).
And thus, Citrahold was created (Citra being the name of the main emulator, -hold because you physically hold your saves within the 3DS).
A save manager (Checkpoint) is still required, but this massively speeds things up.
Citrahold exists as three:
And also Citrahold Server... But if you're here, you likely don't need to worry about that.