A power supply unit (PSU) is a crucial component in electronic devices, converting electrical energy from an outlet into usable power for the device. It ensures that the correct voltage and current are supplied to various parts of the system, such as the motherboard and storage drives. In computers, the PSU typically connects to the motherboard, graphics card, and other peripherals, providing stable power to keep the system running smoothly. Different PSUs vary in wattage, efficiency ratings, and form factors, making it important to choose one that meets the specific needs of the device.