In this review, we introduce a conducting polymer called poly(3,4-ethylenedioxythiophene) (PEDOT), due to its interesting features such as satisfactory conductivity, good transparency, easy processability, low price, small redox potential and good electrochromic properties. We review the synthesis routes, conductivity enhancement methods and applications of PEDOT in industrial and biomedical fields. We also discuss the challenges to use PEDOT such as difficulty in deposition on the electrode surface and conductivity enhancement. PEDOT is the most promising derivative of polythiophene in the cases of physical and chemical stability, conductivity, biocompatibility and transparency. PEDOT is usually paired with polystyrene sulfonate (PSS) to enhance its molecular weight. PEDOT:PSS is an electronically conducting polymer, which is water-soluble causing easy processing.