Peripheral controllers are devices that manage the communication between a computer and its peripheral devices, such as printers, keyboards, and mice. They help ensure that data is transmitted correctly and efficiently, allowing users to interact with their computers seamlessly. These controllers can be built into the computer's motherboard or exist as separate units. Examples include USB controllers for connecting various devices and game controllers that enhance the gaming experience. By facilitating these connections, peripheral controllers play a crucial role in the overall functionality of computer systems.