A PID controller is a type of feedback control system widely used in industrial automation. The acronym "PID" stands for Proportional, Integral, and Derivative, which are the three components that work together to maintain a desired output level. By continuously measuring the difference between a setpoint and the actual output, the PID controller adjusts the control inputs to minimize this error. The Proportional component responds to the current error, the Integral component addresses past errors, and the Derivative component predicts future errors. This combination allows the PID controller to provide stable and accurate control in various applications, such as temperature regulation, speed control, and process automation.