Redundant Array of Independent Disks, or RAID, is a method of keeping content on multiple hard disks at the same time. A RAID can be software or hardware depending on the hard drives that are used - physical or logical ones, still what is common between them is that they all function as one single unit where your information is stored. The top advantage of using a RAID is redundancy because the information on all of the drives shall be identical all of the time, so even in the event that a drive fails for some reason, the information will still be present on the remaining drives. The general performance is also better as the reading and writing processes could be split between a number of drives, so a single one will not be overloaded. There are different types of RAIDs where the capabilities and fault tolerance can vary depending on the specific setup - whether information is written on all of the drives in real time or it is written on a single drive and then mirrored on another, what amount of drives are used for the RAID, etc.
