RAID (Redundant Array of Inexpensive Disks) is a data storage virtualization technology that combines multiple physical disk drive components into one or more logical units for the purposes of data redundancy, performance improvement, or both. The document discusses various RAID levels including RAID 0, 1, 5 and 6 that use techniques like disk striping, mirroring, and parity to provide redundancy and performance benefits over simply grouping disks. It also notes the minimum number of disks required for each level.