Okay kiddo, so you know how sometimes when you are playing a game with your friends, someone needs to be in charge to make sure everyone is playing fair and that there are no problems? Well, that's kind of what a governor-in-chief is.
A governor-in-chief is a person who is in charge of a big group of people, like a whole country. They help make sure that the laws are followed and that everyone is safe and happy.
In some countries, there is a person who is called the governor-in-chief because they are in charge of many things like the military, the economy, and the government. They are like a big boss who makes sure everything is running smoothly.
So basically, a governor-in-chief is like the grown-up in charge of a really big group of people, like a whole country. They have a lot of important jobs to do to keep everyone safe and happy.