Catalysts are substances that speed up chemical reactions by lowering the activation energy required for the reaction to occur. They do this by providing an alternative reaction pathway that has a lower energy barrier than the original pathway. Catalysts are not consumed in the reactions they catalyze, which means they can be used over and over again. This makes them a cost-effective and environmentally friendly way to increase the rate of chemical reactions. There are two main types of catalysts: homogeneous catalysts, which are in the same phase as the reactants, and heterogeneous catalysts, which are in a different phase. Homogeneous catalysts are often easier to control and monitor, while heterogeneous catalysts are easier to separate from the reaction products. Catalysts are widely used in the chemical industry to produce a variety of products, from fuels and plastics to pharmaceuticals and agricultural chemicals. Without catalysts, many important reactions would proceed too slowly to be practical on an industrial scale. In conclusion, catalysts play a crucial role in the efficiency and sustainability of chemical reactions. By providing an alternative reaction pathway with lower energy requirements, catalysts enable faster reactions with higher yields, ultimately benefiting both the industry and the environment.