In process engineering, controllers play a crucial role in maintaining the desired output of a system by adjusting the inputs based on feedback. Different types of controllers are used depending on the nature of the process, desired control performance, and specific requirements of the system. This article provides an overview of the main types of controllers used in process engineering, including Proportional (P), Integral (I), Derivative (D), Proportional-Integral (PI), Proportional-Derivative (PD), Proportional-Integral-Derivative (PID), and advanced control strategies.