RAID 0 is not technically RAID because it does not have any redundancy. RAID 0 is basically a RAID setup that employs the striping mentioned in the above posts.
This setup requires at least two hard drives to be configured into a "striped set". RAID 0 is becoming popular with gamers because it has higher read/write speeds than normal and will really help to speed up a computer. People who are into raw speed for gaming, multimedia, etc, will reap the benifits of RAID 0. But, because it lacks the redundancy factor, it is not used in mission-critical environments. If one drive of the RAID 0 array dies, the whole array is screwed.
Raid 1 is mirrored and will protect data but is much slower than RAID 0
hope this helps
regards
succuba