Substrate:This is the molecule upon which an enzyme acts. In our baking analogy, this would be like the flour for your cake - it's one of the main components needed for the reaction (baking) to occur.
Product:This is what results from a chemical reaction. Using our baking analogy again, this would be your finished cake!
Catalyst:A substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change. It's like adding baking powder to your cake mix - it helps everything come together more quickly and efficiently, but isn't part of the final product.