This charging block was originally packaged as the official power supply for retro micro-consoles like the NES Classic Edition and the Super NES Classic Edition. It provides a standard 5V / 1.5A (7.5W) power output.
Compatibility:
While it was bundled with the classic mini consoles, it is also officially supported by Nintendo for powering and charging a variety of accessories using a standard USB-A to USB-C or micro-USB minicable:
Nintendo Switch Pro Controllers
Joy-Con Charging Grips
Poké Ball Plus accessories
Note: While you can use it to slowly charge a Nintendo Switch console or Nintendo Switch Lite in handheld mode, it does not provide enough power to support the Nintendo Switch Dock for TV mode.