Stands for “Power Supply Unit,” is the main component that handles power converting from AC to DC and delivering optimized voltages and currents to other parts of a computer.

For desktop PC and AIO, the PSU is usually an internal component that offers an outlet to connect to an AC power source and multiple DC outputs with different interfaces to connect other parts of a mainboard, fans, hard drives, and more. As an example, Surface Studio has a PSU that is located inside the base.

Surface Studio PSU

Surface Studio PSU (Image source: AliExpress)

For Surface laptops, tablets, and phones, the PSU must separate from the chassis to reduce the weight and thickness of the device. In this case, the PSU is called a power adapter.

Surface Laptop 3 PSU

Surface Laptop 3 PSU (By Evan Forrest @SurfaceTip)