RAID 0 = striping, theoretically increases performance by splitting a file between two or more drives which each simultaneously read/write instead of one drive doing all the work (not recommended for use on a personal desktop). If one drive fails, however, all info on both drives is lost. Performance gains are usually very slight, if any, on a personal desktop (see Anandtech's article on RAID 0).
RAID 1 = Mirroring/duplexing, which creates an identical copy of one drive onto another, strictly used for fault tolerance, not a true backup solution.
RAID 5 = striping with parity, requires at least 3 drives, two which stripe, and the third stores a parity bit for error detection (which two drives stripe and which stores parity is different for each file), but can still suffer the same failure issues as a RAID 0 setup.
RAID 0+1 = striping with mirroring, requires 4 drives, basically gives fault tolerance to a RAID 0 setup, but requires a second set of drives for mirroring. Very expensive due to the number of disks required, but theoretically gives the best of both worlds.
Does this help?