An I/O Controller is a hardware component that manages the input and output operations of a computer system. It acts as an intermediary between the central processing unit (CPU) and peripheral devices, such as keyboards, mice, printers, and storage drives. By coordinating data transfer, the I/O controller ensures that the CPU can efficiently communicate with these devices without being overwhelmed by the volume of data. The I/O controller can be found in various forms, including disk controllers for hard drives and USB controllers for connecting external devices. It helps optimize performance by handling multiple data streams and prioritizing tasks, allowing the system to operate smoothly and effectively.