It is a core part of the "NoNpDRM" framework, which allows legitimate Vita content to run on modified hardware or emulators.
If you own a hacked PS Vita, the NoNpDRM plugin automatically generates a work.bin file when you run a game from a cartridge or a legitimate digital purchase. This can then be transferred to your PC for use with Vita3K. How to Install Games Using Work.bin To use a work.bin file in Vita3K, follow these steps: Vita3k Work.bin File
Most users obtain these files from community-maintained databases that store license information for preserved Vita software. It is a core part of the "NoNpDRM"