Catalyst poisoning occurs when a substance, known as a poison, binds to a catalyst and reduces its effectiveness. Catalysts are materials that speed up chemical reactions without being consumed in the process. When a poison attaches to the active sites of a catalyst, it prevents the intended reactants from interacting, leading to decreased reaction rates and efficiency. This phenomenon is significant in various industrial processes, such as those involving catalytic converters in vehicles or chemical manufacturing. Understanding catalyst poisoning helps in developing better catalysts and finding ways to mitigate the effects of poisons, ensuring optimal performance in chemical reactions.