Okay kiddo, so a Zen Master is like a really wise person who knows a lot about a certain kind of meditation called Zen. They have studied it for a very long time and can teach other people how to do it too.
They are very peaceful and patient, and they try to help others find their own inner peace and happiness. They often live in temples or other quiet places where they can focus on their practice and help others who come to learn from them.
Just like a teacher at school, a Zen Master can help show you the way and guide you, but you ultimately have to do the work yourself to become better at Zen meditation. They are kind of like a superhero when it comes to knowing how to be calm, patient and kind.