Okay kiddo, so you know how different groups of people have leaders who they look up to and listen to, like a teacher or a parent? Well, the Master of the Order of Preachers is like the leader of a special group of religious people called the Dominicans.
The Dominicans are a group of men who dedicate their lives to serving God and helping other people understand and follow God's teachings. The Master of the Order is like their boss or leader, but he doesn't just tell them what to do. He helps them figure out how to do their jobs better and makes sure they all work together to achieve their goals.
The Master of the Order is chosen by the other Dominicans to lead them because he is very smart and wise, and he has proven that he can help them do a good job. He also knows a lot about God and the Bible, and he helps the other Dominicans understand these things better so they can share them with other people.
Overall, the Master of the Order of Preachers is a very important person who helps the Dominicans serve God and spread His message to people all over the world.