The theoretical foundations of electrochemistry are presented at the modern level; basic concepts and definitions based on uniform terminology, taking into account IUPAC recommendations, electrochemistry of solutions and melts, electrode potentials, structure of interphase boundaries, thermodynamics and kinetics of electrochemical processes, as well as applied aspects of electrochemistry - chemical current sources and electrochemical reactors, corrosion and deposition of metals, redox reactions and electrochemical methods of analysis.