Enzymes are proteinous biochemical molecules that serve as catalyst in living systems. They speed up the rate of biochemical reactions by lowering the activation energy of the reaction they are involved in.
As this question describes, enzymes possess an active site, which the substrate binds to yield products. The enzymes make the reaction faster by reducing the activation energy of the reaction, which is the energy needed to start a reaction.
A specific type of cancer is diagnosed by taking the number of diagnoses of that certain cancer type and dividing it by the total number of cancer diagnoses.