So imagine that you are playing in a game with all your friends, and you are trying to pick a leader to make all the important decisions. In the game, the leader is called the "Prince."
Now, in the Catholic Church, there are a bunch of people who are really important because they help make big decisions about how the Church should be run. These important people are called "Cardinals."
But some Cardinals are so important and respected that they get a special title: "Prince of the Church." It's like being the best player in the game and getting a special medal or trophy.
Being a Prince of the Church means that you have a lot of wisdom and knowledge about the teachings of the Church, and that you are trusted to help make important decisions about things like who should be the next Pope. So it's a big honor and responsibility, kind of like being a leader in a game!