These are the plug-in sockets used to hook up devices such as modems, mice, printers, etc. It's a good idea to have expansion room. Parallel ports accept cables that have parallel wires, letting data flow through the cable at a high speed. This type of port is most often used to connect peripherals such as a printer. Parallel ports are commonly referred to as LPT1 or LPT2.
Serial ports are sockets where cables attach a serial device such a mouse, a scanner, or a modem.
Only one bit of data can be transferred through this port at a time, while parallel ports can transfer an entire byte. In addition to the usual serial and parallel ports, USB ports are a new kind of port that make it much easier to hook up many newer models of peripheral equipment. If you're planning to transfer a lot of video to and from your PC, look for an even faster new port called variously 1394, FireWire, or I-link, which runs about 30 times faster than a USB connection. This determines how powerful your computer is, and also how much it will cost. One hertz is equal to one cycle per second, while 1MHz is equal to one million cycles per second.