Both FireWire and USB seem to be computer services that the designers have gotten right. When you plug a cable from either type of interface into your computer, you can realistically expect the device connected to that cable to work.
A USB interface can control just about everything from a simple input device like a mouse or keyboard that transfers just a few bits at a time, to a multimedia player or network connection that streams several megabytes per second. Each USB host can support several simultaneous USB connections.
FireWire (IEEE 1394) is used most widely with camcorders, audio consoles, and other high-bandwidth multimedia devices, but it can also connect disk drives, printers, and other peripherals. Unlike USB, a 1394 bus does not require a controller in a host computer; each device controls its own connection.