WiinUPro is a program that allows you to use your Nintendo branded Bluetooth enabled devices with your computer.
With it, you can use your Wii U Pro Controller, Wiimotes and extensions, Switch Joy-Cons, and Switch Pro Controller as input devices to play your PC games. The name derives from an odd combination of Wii U, Windows, and Pro Controller (I pronounce it like win-you-pro) and was created before the Nintendo Switch was a thing.