Alternatively referred to as IEEE-1394, FireWire is a digital bus with a bandwidth of 400-800 Mbps. It can handle up to 63 units on the same bus, and is hot swappable. It was first developed by Apple in 1995.
Users more familiar with USB can consider FireWire similar to USB, as they has many similarities. Like USB, FireWire has dozens of different devices such as removable drives and cameras.
Ports labeled as i.Link are Sony's implementation of IEEE-1394.