A RAID controller is a hardware or software component that manages a RAID (Redundant Array of Independent Disks) setup. Its primary function is to combine multiple hard drives into a single unit to improve performance, increase storage capacity, or provide data redundancy. This helps protect against data loss in case of a drive failure. RAID controllers can be found in servers and high-performance computers, and they come in two main types: hardware RAID controllers and software RAID controllers. Hardware controllers use dedicated processors to manage the RAID array, while software controllers rely on the computer's operating system. Both types help ensure data integrity and optimize storage efficiency.