FireWire, also known as IEEE 1394, is not the kind of cable you’ll typically find these days. Popularized in the early 90s, it has long been a competing standard for USB, not unlike Thunderbolt today. Offering much faster speeds, even faster than USB 2.0, FireWire is the connection you typically find on older external hard drives and digital cameras.
FireWire 800 vs 400
FireWire has two versions, and unlike USB 2.0 and 3.0, they are not backward compatible. They don’t even look alike, which can lead to some confusion. The older standard, FireWire 400, is a flatter connector with one rounded side, while the faster 800 version resembles a fat USB connector.