"homogeneous catalysis is a sequence of reactions that involve a catalyst in the same phase as the reactants. Most commonly, a homogeneous catalyst is codissolved in a solvent with the reactants... HeteroGeneous catalysis where the catalyst is in a different phase (ie. solid, liquid and gas, but also oil and water) to the reactants. Heterogeneous catalysts provide a medium (usually, a surface) on which the reaction may take place" (Wiki)
