Among all conducting polymers, PEDOT or poly(3,4-ethylenedioxythiophene) has a special place within the field of organic electronics due to its outstanding conductivity, stability, and processability. Since PEDOT was first synthesized in the late 1980s, a massive amount of knowledge has been accumulated about its morphological, structural, electrical, and optical properties, along with its applications in various devices. Notably, however, is that the vast majority of the reports in the field are purely experimental, without any theoretical support from simulation and modeling. In many other fields of material science, molecular modeling has already become a standard tool for guiding the experimental work. For PEDOT, the lack of the theoretical understanding of many important aspects of the material properties and device functionality leads to misconceptions and controversial issues hindering the progress in the field. The purpose of this Perspective is to fill the knowledge gaps and to present the current state-of-the art of the theoretical understanding of PEDOT. As theoretical understanding is essential to correctly interpretate experimental results and for the design of materials and devices with better performance, this Perspective targets equally experimental and theoretical communities working on PEDOT and related materials. We also hope that this Perspective will attract further attention of the computational community, which would help to bring the theoretical understanding of PEDOT to the levels already achieved in many other fields of material science.