its used fer gettin ridda them danged ol' bee's nests!
Oh..Heh..
I'm not completely knowledgeable on this either, but I'll give it a shot and tell you what I do know.
RAID stands for Redundant Array of Independent Disk.
They can be used to make 2 drives act as one, or mirror one drive using the second drive.
There are varying levels of RAID, but the most popular are 0 and 1. RAID 0 (Striped) is two disks acting as one. For example 2x500GB hard-drives would create 1 terabyte of data storage. Since you have two heads reading/writing information, you increase the performance because of the better bandwidth. If one drive fails, data on both drives are lost.
RAID 1 (Mirrored) is one disk creating a duplicate copy of the other. For example 2x500GB hard-drives in a RAID 1 array would allow you to have data security. If one drive fails, you have a duplicate drive still working. Replace the defective hard-drive, let the mirror rebuild, and you're set.
There are some higher ones like 3, 4, 5, and 6, but I don't know much about those, except that some of those levels have parity.
Then there are the variations (or nested RAID) of it, such as RAID 0+1 or RAID 1+0.
RAID 0+1 would be a striped mirror. Four drives are needed. 2 drives are striped together, and 2 drives are mirroring those first 2.
Some of the more advanced information on RAID, like RAID 3, 4, 5, 6, 0+1, etc is on Wikipedia.
Standard RAID levels, then underneath that is more information on Nested levels, like 0+1, etc.
RAID 0 - faster transfer speeds possible but a bit more latency. It doesn't shine nearly as much in Desktop use as it does in Workstation/Servers. Also less reliable (double the chance of failure).
RAID 1 - It's to keep a computer up and running if one drive dies. Basically opposite goal of RAID 0. But not to be used as means for backup. (If something happens to your PC as a whole your files are screwed on both drives)