What is meant by the catalytic promoter and catalytic poison?

Catalytic promoter – Those substances which are added with catalysts in a chemical reaction to increase the efficiency or activity of the catalyst is known as the catalytic promoter.
Example:

N₂ + 3H₂ 2NH₃
In Haber’s process for the synthesis of ammonia, traces of molybdenum increases the activity of finely divided iron which acts as a catalyst hence, acts like a catalytic promoter.
Catalytic poison - Those substances which are added with catalysts in a chemical reaction to decrease the efficiency or activity of the catalyst are known as a catalytic poison.

Example:

N₂ + 3H₂ 2NH₃

In the above reaction of synthesis of ammonia carbon monoxide decreases the efficiency of the iron catalyst and hence, acts like a catalytic poison.