Hey kiddo, do you know what a stockpile is? It's when you gather a bunch of things to keep them safe or use them later.
Now, nuclear means something related to an atom and its tiny parts called nuclei. These tiny parts release a lot of energy when they break apart or come together. Scientists figured out how to use this energy to make really powerful bombs called nuclear weapons.
A nuclear stockpile is when a country gathers and keeps a bunch of these nuclear weapons. Some countries have a lot of them, and some have just a few. And they keep them safe and secure so nobody else can get to them.
Some people think having a nuclear stockpile is important for a country's safety, like a big stick to protect against enemies. But other people think it's dangerous because if something goes wrong, like an accident or mistake, it could cause a lot of harm and destruction. So it's something countries have to be very careful with.