A Tour Inside a Desktop PC : Inside the Case
Understanding how the many parts of a computer connect to each other inside your PC begins with the case, which physically houses most of the components.
Power Supply: The power supply connects to nearly every device in the PC to provide power. It is located at the rear of the case.
Drive Bays: The 5.25" and 3.5" drive bays house the many kinds of storage devices a computer might contain.
Expansion Slots: The expansion slots at the rear of the case are specially cut out so the peripherals connected to the motherboard can extend from the case for easy connection to external devices such as printers, monitors and other external devices.