I am often asked by clients what RAID (Redundant Array of Independent Disks) is? In short, RAID is a configuration of hard drives (storage) that your computer uses. Most computers have one or two hard drives in them. This is where your programs are installed and your data is saved (documents, pictures, music, etc.).
RAID systems allow for many hard drives to be connected together to allow for more storage and also can be configured for redundancy (in the event a drive fails). There are many types of RAID configurations, the most common are RAID 5 & RAID 6. Below is a link to an article that helps demystify all the various configurations that you can use with a RAID system and also will calculate how much storage space you can have by adding multiple drives and the size of the drives.