Citra was a 3DS emulator which was originally created in April 2014, and continued to see regular updates until February this year.
The core Citra team went on to create the Switch emulator Yuzu, and earlier this week a Nintendo lawsuit settlement saw the Yuzu team agreeing to pay $2.4 million in damages and permanently stop offering or marketing Yuzu or its source code.
However, the settlement has seen a similar shutdown for the Citra emulator too, a move which some commentators suggest is a blow for game preservation.
I've heard of these but never used them. They seem to have outlived their usefulness in terms of where you actually should be playing these games legally! Development though: I don't care if it's on PC.
