The design of the feedback control system is profoundly influenced by the paradigm shift brought about by active disturbance rejection control. It effectively mitigates the impact of modeling errors and process parameter variations, thereby establishing itself as a valuable asset for control engineering professionals. Its tuning method is straightforward. This paper intends to provide foundational information on observer-based linear ADRC for the intended audience. In this paper for evaluation of ADRC, a simulative study is carried out using first- and second-order processes for the practitioners. This paper presents investigation into the impact of variation in process parameters, demonstrating that ADRC adapts severe parameter variations without relying on the exact mathematical model of the physical process. It illustrates the capabilities of the ADRC in the presence of varying process parameters or structural uncertainties. The simulation results demonstrate the robustness of linear ADRC in the presence of varying uncertainties. The performance comparison of the linear active disturbance rejection controller (LADRC), PI controller, and PID controller is presented in this paper showing that former is more superior. Also, linear ADRC achieves better performance in effectively rejecting external disturbances than PI and PID Controllers.