A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. Catalysts work by providing an alternative reaction pathway with lower activation energy, allowing the reaction to occur more quickly or at a lower temperature. Catalysts are widely used in industrial processes to increase efficiency and reduce energy consumption, as well as in various other fields such as environmental remediation, pharmaceuticals, and energy production. Researchers study catalysts to understand their mechanisms and develop new catalyst materials with improved performance and selectivity.