The adapter cards add extra functionality to a computer and are designed for a specific task. There are several typed of adapter cards: Input/Output cards, Storage Controllers, Sound Cards,Graphic cards,...
A RAID (Redundant Array of Independent Diskscard) (or RAID controller) is an adapter card in a PC that provides data fault tolerance. It controls the expansion of internal and external drives so they can work as a single logical unit and provides fault tolerance for storage devices