Firewire is also known as I-link or IEEE1394 and is high speed (400Mbps). Almost standard on all Digital Video Cameras and offers a standardised easy to use plug and play method of connecting peripherals to your PC/Mac. Slightly slower than USBv2 (480Mbps) but often more reliable which comes from the internationally recognised standard (IEEE). IEEE1394b is available which is twice as fast (800Mbps). The 6 connector on Firewire is the standard for most PC s and is a larger block
The 4 connector on Firewire is the smaller connection 6 to 4 usually connects the DV-out on a video camera to most PC s with Firewire ports (PCI and PCMCIA cards are available) and some other video editing devices. It can also be used for other peripheral connection (some Firewire scanners external drives etc). Check devices documentation for more details.