PID without a PhD

What is a PID controller?
A proportional-integral-derivative controller is a generic control loop feedback mechanism (controller). A PID controller attempts to correct the error between a measured process variable and a desired setpoint by calculating and then outputting a corrective action that can adjust the process accordingly and rapidly, to keep the error minimal.

The PID controller calculation or algorithm involves three separate parameters: the proportional, the integral and derivative values.

The proportional value determines the reaction to the current error, the integral value determines the reaction based on the sum of recent errors, and the derivative value determines the reaction based on the rate at which the error has been changing. The weighted sum of these three is used to adjust the process.