Well, did you know that sometimes people can be mad at each other? It's okay, even grown-ups have fights sometimes! When people have fights, they can become what we call "enemies."
Now, have you ever heard the saying, "keep your friends close, but your enemies closer"? That's because sometimes, even when two people are fighting, they can still learn things from each other or help each other out, even if they don't always get along.
So, "best enemies" means that two people who are enemies, but they still understand and try to help each other out when they can. It's like when two superheroes, like Batman and The Joker, are always fighting, but they still have a kind of respect for each other and might even team up to stop a bigger bad guy.