The Power Supply Unit, abbreviated PSU, is what distributes the power across the PC via a variety of connectors.
Modern ATX Motherboards have a 20-Pin 12v Connector, extended to a 24-Pin one for PCI-Express Motherboards, as well as a dedicated 12v 4-Pin Connector for the CPU itself. Older Slot Processors also had a connector specifically for the CPU.
Also present are 4-Pin Molex connectors, used for connecting IDE Devices, and a smaller 4-Pin connector for connecting a floppy drive.