The power cord is the link between the power outlet and the power supply unit in the computer casing. If the power cord is not plugged in, the computer will not power on. To protect your computer from voltage spikes, you can plug the power cord into a surge protector. You can also use an Uninterruptable Power Supply (UPS), which acts as a surge protector and also provides temporary power if there is a blackout.
USB Port: Mouse, Keyboard, Camera, Printer, Flash Drive (Thumb Drive)
In the past, we stored data on a Floppy Disk, then later a CD or DVD. Most convenient now is a Thumb Drive.