Catalysis

Catalysts are substances that make reactions proceed faster without reacting themselves. Think of a catalyst like a person pushing a cart down a hill. The person is helping the cart go down the hill faster but not experiencing the force down the hill themselves.

Catalysts make the reaction proceed faster by providing the reaction with an alternative mechanism that has a lower activation energy. By the Arrhenius Equation, decreasing the activation energy's magnitude increases the reaction rate constant.

You can see this in the image, where adding a catalyst(blue) alternates the reaction mechanism into a 2-step mechanism that has a lower transition state and thus activation energy.