So, let's pretend you're a little kid named Timmy. Now let's say something happened and your mom and dad can't take care of you anymore. Maybe they got sick or something.
When that happens, a judge might decide that you need someone to take care of you until your mom and dad can take care of you again. That person is called a "guardian."
When a judge makes you a ward of court, that means the judge is taking care of you. The judge decides where you will live, who takes care of you, and makes sure you are safe and healthy.
Being a ward of court isn't always easy or fun, but it's important because it keeps you safe and cared for until your mom and dad can take care of you again.