RAID For Dummies: No, it's not an Insecticide
Bjorn3D just pubbed this excellent guide explaining how RAID works, its history and terminology. If you never heard about RAID, this guide should help you understand what it is all about, and if your already a RAID pro, you should read it anyways. I'm pretty sure you'll learn a thing or two out of it.
"The use of RAID, a Redundant Array of Inexpensive Disks, up until a few years ago was pretty much limited to servers and high end workstations; this was primarily due to the cost of the controller and the accompanying hard drives. Today that's not at all the case! Most of the newer motherboards provide one or more onboard RAID controllers capable of delivering configurations up to and including RAID 5. With the cost of disk storage at an all time low the two primary barriers to using this once esoteric form of data storage have been lifted."