When things vibrate, they can make other things vibrate too. It's like when you tap on a drum, it makes the air vibrate and you can hear the sound. This is called resonance.
Catalytic resonance theory is when certain molecules get excited by vibration and then can make other molecules around them vibrate too. Imagine a playground where one kid starts jumping on the trampoline and then other kids start jumping too. The excited molecule is the first kid and the other molecules are the followers.
This process is really important in chemistry because it helps reactions happen faster. It's like if you needed to build a tower of blocks, it would take a lot longer if you had to do it one block at a time. But if you had help from other people, you could build it much faster. Catalytic resonance theory is like having helpers in chemistry reactions.
So basically, catalytic resonance theory is when vibrations in molecules can make other molecules vibrate too, which can help reactions happen faster.