What substances are called catalysts? What reaction used to obtain oxygen is carried out in the presence

What substances are called catalysts? What reaction used to obtain oxygen is carried out in the presence of manganese oxide (tetravalent)? Write the equation of this reaction

A catalyst is a substance that increases the rate of reaction without being consumed. Enzymes are natural catalysts responsible for many essential biochemical reactions.
Most solid catalysts are metals or oxides, sulfides and halides of metallic elements and semi-metallic elements – boron, aluminum and silicon. Gaseous and liquid catalysts are usually used neat or in combination with suitable carriers or solvents; solid catalysts are usually dispersed in other materials known as catalyst carriers.