No first use

Okay, kiddo, let me explain what "no first use" means.

Have you ever played a game of tag and decided not to be the one who starts chasing others first? This is similar to what "no first use" means. It's like an agreement among grown-ups, especially between countries with nuclear weapons, that they won't be the first ones to use their nuclear weapons in a conflict.

Just like in a game of tag, it is always better to avoid getting into conflicts, but if it happens, we should try to avoid using weapons that can cause severe damage. And the grown-ups running countries with nuclear weapons understand that using such weapons could cause massive destruction and loss of life that cannot be undone.

So, they agree that if someone else uses nuclear weapons, they may retaliate, but if they don't use them first, they are keeping the situation under control and avoiding a devastating war. It's like a rule that everyone agrees to follow to ensure peace and safety.

I hope that explains what "no first use" means, and you understood it!