How does a catalyst work?

A catalyst actually decreases the activation energy of a reaction in 2 ways:

1) By a process called adsorption, it attracts the molecules of the reactants to its surface so that they are closer together and can react more easily by colliding more successfully.

2) It creates a transition state, which is an inter mediate state before the final reaction occurs, which creates an intermediate, unstable compound using the catalyst itself. By the time the final product is formed, a new product as well as the original catalysy are remaining and the activation energy is considerably reduced.