RAID stands for "Redundant Arrays of Inexpensive Disks", and is a computer storage system that involves combining a number of small capacity (small amount of storage) hard drives, into an array, with better performance results than a single large capacity hard drive.
There are 5 different 'redundant' levels of RAID (RAID-1 to RAID-5) configuration, each with varying features and performance, as well as an additional 'non-redundant' RAID-0 configuration.
The process of "striping" involves a chunk of data being broken up into smaller parts and saved across a number of drives. For example; a chunk of data is to be saved across 4 drives, depending on the chunk size, it would be broken up into a number of pieces (in this case, lets say 8), called A, B, C, D, E, F, G and H, and stored across the drives.
RAID levels 1-5 offer protection against data loss and corruption, by either having the entire drive "mirrored" (an exact copy stored) on another disk in the array, or by having parts of each piece of data stored either on the same or another disk, to verify the data is correct.
RAID-0 only uses striping, and does not offer data verification.
RAID storage is theoretically much faster than using single drives, as four times the amount of data can be read/written to/from the RAID than a single drive. This system of storage is much cheaper than a single drive that would yield the same capacity and performance.
RAID storage in a server environment, or any other with high disk usage (such as multimedia development) would greatly increase performance and data integrity, by lowering the time taken to access/write data to and from the system.