Electrochemistry is a branch of chemistry that studies chemical reactions which take place in a solution at the interface of an electron conductor (a metal or a semiconductor) and an ionic conductor (the electrolyte), and which involve electron transfer between the electrode and the electrolyte or species in solution.
If a chemical reaction is driven by an external applied voltage, as in electrolysis, or if a voltage is created by a chemical reaction as in a battery, it is an electrochemical reaction. In contrast, chemical reactions where electrons are transferred between molecules are called oxidation / reduction (redox) reactions. In general, electrochemistry deals with situations where oxidation and reduction reactions are separated in space or time, connected by an external electric circuit to understand each process.
"Macvicar's illustrations of assimilation "Attraction, inertia, elasticity, heredity, reversion, symmetry, culminating in sphericity or symmetrical cellularity, chemical and electrical action, especially in voltaic action the influence and persistence of this law is most remarkably displayed." [JOHN ERNST WORRELL KEELY]