There are three main types of catalysts – homogenous catalysts, heterogeneous catalysts, and biocatalysts.

• Catalysts that are in the same phase as the reactants are known as homogenous catalysts. 
• Catalysts that are in a phase that’s different from the reactants are known as heterogeneous catalysts.
• When the reaction is catalyzed by one of the reactants, that catalyst is known as a biocatalyst or enzyme.