You know how sometimes, when you're playing a game with your friends and one of them doesn't show up, you start playing without them? And if they don't come back, you keep playing without them and they lose the game?
Well, that's kind of like what happens with a default judgment. When people go to court, they have to follow certain rules and be there at certain times. If someone doesn't follow the rules or doesn't show up to court, the other side can ask the judge to give them a default judgment.
This means that the person who didn't follow the rules or show up to court automatically loses the case. It's kind of like the other side winning by default because the person who didn't show up or follow the rules isn't there to defend themselves or explain their side of the story.
It's important to follow the rules and show up to court so you don't lose by default!