If you have a printer connected to your computer, there is a good chance that it uses the parallel port. While USB is becoming increasingly popular, the parallel port is still a commonly used interface for printers.
A typical parallel port on the back of your computer
Parallel ports can be used to connect a host of popular computer peripherals:
In this edition of HowStuffWorks, you will learn why it is called the parallel port, what it does and exactly how it operates.