Another explanation is that catalysts participate in chemical reactions. In an overall chemical reaction, the role of a catalyst is to lower the activation energy required for the reaction to occur. Essentially, it transforms a relatively difficult reaction into two easily occurring chemical reactions (the opposite is called an inhibitor). In these two reactions, the catalyst acts as a reactant in the first reaction and as a product in the second. Therefore, from the perspective of the overall reaction equation, the catalyst remains unchanged before and after the reaction.
Generally speaking, a catalyst is a substance that participates in the intermediate process of a chemical reaction, selectively alters the rate of the reaction, while its quantity and chemical properties remain essentially unchanged before and after the reaction. The effect of a catalyst in accelerating a chemical reaction and bringing it to chemical equilibrium as quickly as possible is usually called catalysis, but it does not change the equilibrium of the reaction.
