Here's a breakdown:

* Catalyst: A substance that speeds up a chemical reaction without being consumed in the process.

* Substrate: The reactant that the catalyst interacts with.

The catalyst provides a different reaction pathway with lower activation energy, allowing the substrate to react more easily and quickly. The substrate binds to the catalyst's active site, where the reaction occurs.

For example, in the enzyme-catalyzed breakdown of hydrogen peroxide, the enzyme catalase acts as the catalyst and hydrogen peroxide is the substrate.

Let me know if you have any other questions.