Okay, kiddo, do you know what extradition means? It's when one country sends one of its people (like a criminal) to another country where they're wanted for doing something bad.
So in the United States, if someone commits a crime (like stealing or hurting someone) and then goes to another country (like Mexico), the US can ask that country (Mexico) to send that person back to the US to face punishment.
But it's not just automatic -- the two countries have to agree to the extradition. And there are a bunch of rules about what kinds of crimes can be the subject of extradition requests.
This can sometimes be complicated and take a while, but basically that's how it works. It's like asking a friend to borrow a toy they took instead of asking their parents, but instead it's countries and criminals.