A RAID controller is a hardware or software component that manages the Redundant Array of Independent Disks (RAID) configuration in a computer system. Its primary function is to combine multiple hard drives into a single unit, improving data redundancy and performance. By distributing data across several disks, it helps protect against data loss in case one drive fails. In addition to data protection, a RAID controller can enhance read and write speeds by allowing simultaneous access to multiple drives. It can be found in servers, workstations, and high-performance computers, making it essential for businesses that require reliable data storage solutions.