What kind of reaction takes place when a catalyst is used?

When a catalyst is used in a chemical reaction, it facilitates the reaction without undergoing any permanent change itself. This means that, while the catalyst helps lower the activation energy required for the reaction to proceed, it remains unchanged at the end of the reaction and can be used again in future reactions. Therefore, the essence of a catalytic reaction is that the catalyst is not consumed during the process, allowing it to continuously assist in the transformation of reactants to products over multiple reaction cycles.

This characteristic distinguishes catalytic reactions from non-catalytic processes in which the reactants or conditions can change the course of the reaction or lead to a depletion of the materials involved.