IEEE 1394 4-Pin (Right), and IEEE-1394a 6-Pin (Left)
FireWire, also known as IEEE 1394, was designed to be a universal interconnect, eliminating the need for many different input/output connectors. The 1394 bus is a versatile, high speed, and inexpensive way to connect a wide variety of consumer electronic devices such as computers, digital camcorders, hard drives, scanners, printers, audio recorders, and videoconferencing cameras. With FireWire, it's possible to connect up to 63 devices together. When 1394.1 bus bridges become available, it will be possible to connect over 60,000 devices together on a common bus.
There are currently two standards: the original FireWire, now referred to as FireWire 400 or IEEE 1394, and FireWire 800 or IEEE 1394b. As the names imply, the maximum speed of FireWire 400 is 400 Mbits per second, whereas FireWire 800 tops out at 800 Mbits per second. FireWire 800 is backwards-compatible, and unlike USB the FireWire bus speed is not diminished when a slower FireWire 400 device shares a FireWire 800 bus. The maximum cable length is currently 4.5 meters or around 15 feet.
We also have IEEE 1394b (FireWire) cables.