What is a catalyst? What is an inhibitor?

(N/A) Catalyst: $A$ catalyst is a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change. For example,$MnO_{2}$ acts as a catalyst in the following reaction to increase its rate significantly:
$2KClO_{3} \xrightarrow{MnO_{2}} 2KCl + 3O_{2}$
Inhibitor: When an added substance reduces the rate of a chemical reaction,it is called an inhibitor. The term catalyst should not be used to describe an inhibitor.