Short for Redundant Array of Independent (or Inexpensive) Disks, a category of disk drives that employ two or more drives in combination for fault tolerance and performance. RAID disk drives are used frequently on servers but aren't generally necessary for personal computers. There are number of different RAID levels. The three most common are 0, 3, and 5.
RAID
Meaning of RAID in English
DAX English glossary of key connectivity terms. Английский глоссарий основных терминов по коммуникациям DAX. 2012