In open court

When you think of a court, like on TV or in books, it's a place where people go to solve problems or argue about something. In open court means that anyone is allowed to come and watch what's happening. It's like when you have a birthday party and your friends can come and watch you open your presents. Only instead of presents, people are talking about important things and a judge is there to help make decisions. Everyone has to be on their best behavior so they don't get in trouble or kicked out of court.