A reaction mechanism is a detailed description of the step-by-step process by which a chemical reaction occurs. It outlines the sequence of elementary steps, including the formation and breaking of bonds, the movement of electrons, and the transition states involved. Understanding these mechanisms helps chemists predict the products of reactions and the conditions needed for them to occur. Each elementary step in a reaction mechanism can involve different types of interactions, such as nucleophilic attacks or proton transfers. By studying these steps, scientists can gain insights into the kinetics and dynamics of reactions, which are essential for fields like organic chemistry and biochemistry.