Difei,
The major difference without writing a small book here is that with box/box (also know as active/passive) redundancy, one box is up and active, while the second box is completly down and not active from an ip or interface perspective.
With VIP and interface redundancy, one CSS is active and considered Primary, while the second box is considered backup but is able to L2 forward requests should they come into the box and get them to the necessary destination.
Pete Knoops
Cisco Systems
