In short, it's just like USB in that data is sent serially bit-by-bit on a small number of wires. Firewire adds layers of protocols and interfaces to make it a "standard".
I find both USB and Firewire to be useful but just like Ford and Chevy, both can move data in the PC and the cars get you from here to there.
Best of luck,
Bob
Can someone explain Firewire in simple language? What are the advantages of having it?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic