Okay kiddo, so imagine there's a big group of people who work together to protect our country. They are called the military. Just like in school, there are rules that everyone has to follow. These rules are called the law.
But, because the military does some really important and dangerous work, they have their own set of rules that are a little different from the regular laws that you and I follow. This is called military justice.
Military justice makes sure that everyone in the military is following the rules and doing their job the right way. It's kind of like when your teacher makes sure that everyone in your class is behaving and doing their work.
If someone in the military breaks one of these special rules, military justice decides what happens next. They have their own court system, which is kind of like a special classroom where people go when they do something wrong.
The people in charge of military justice are called judges and lawyers. They're like the principal and teachers in your school, making sure everyone is behaving and following the rules.
So in summary, military justice is a set of special rules that the military has to follow, and a system in place to make sure those rules are being followed by everyone. If someone breaks one of those rules, military justice decides what happens next.