Okay kiddo, this is all about a big grown-up thing called "collateral estoppel." It's like a game where you win something and then you can't play again to win the same thing.
Let's say you play a game of checkers with your friend and you win. That means you can't play that same game of checkers again to win the same thing, right? The same idea applies to collateral estoppel.
Collateral estoppel is a legal concept that means if a court has already made a decision in a case, then that decision can't be challenged again in another case with the same parties or issues. It's like winning the game of checkers - you can't play again to win the same thing.
For example, let's say there was a court case about a car accident. The court decided that the driver of the car was at fault. Later, there's another court case about the same accident, but with different people involved. The person suing tries to argue that the driver wasn't at fault, but the court can't hear that argument because it's already been decided in the first case.
Overall, collateral estoppel helps save time and resources by preventing parties from re-litigating the same issues over and over again. It's like winning the game of checkers and moving on to play something else.