A short review of the development and achievement of electrocatalysis in the last 50 years is given. The need for the knowledge of the reaction mechanism and position of the rate determining step for rational choice of catalyst is particularly stressed. Fundamental aspects of electrocatalysis are elaborated in more detail on the examples of electrochemically important reactions of hydrogen evolution and oxygen reduction, as well on the reaction of electrochemical oxidation of organic fuels (e.g., methanol).