Catalyst is a substance that speeds up a chemical reaction, or lowers the temperature or pressure needed to start one, without itself being consumed during the reaction. Catalysis is the process of adding a catalyst to facilitate a reaction. During a chemical reaction, the bonds between the atoms in molecules are broken, rearranged, and rebuilt, recombining the atoms into new molecules.

Catalysts make this process more efficient by lowering the activation energy, which is the energy barrier that must be surmounted for a chemical reaction to occur. As a result, catalysts make it easier for atoms to break and form chemical bonds to produce new combinations and new substances. Using catalysts leads to faster, more energy-efficient chemical reactions.

Catalysts also have a key property called selectivity, by which they can direct a reaction to increase the amount of desired product and reduce the amount of unwanted byproducts. They can produce entirely new materials with entirely new potential uses.