If you own a modded Switch, there are guides available on how to dump your own keys to use with your backups on your PC.
I notice you're asking about — this typically refers to production keys for a specific system (often Nintendo Switch, given the version-numbering pattern like “2101” corresponding to a particular Horizon OS or key generation). prod keys v2101
Place both prod.keys and title.keys (if you have them) into this folder. Restart the emulator. If you own a modded Switch, there are
When you see prod.keys v2101 , it means the key file was dumped from a console running firmware 21.0.1 or was manually updated to include the key revisions present in that firmware. Restart the emulator
Specialists recovering data from a dead Switch or a corrupted NAND backup will need the exact prod.keys that match the backup’s firmware version. v2101 becomes a specific search for recovery purposes.