Nuclear proliferation is when a country starts to develop and spread nuclear weapons. Nuclear weapons are very dangerous and powerful bombs that use nuclear energy to release a huge amount of energy, which can destroy a lot of things. If a country starts making nuclear weapons, it could lead to other countries around them also making them, and this can quickly spiral out of control. This can create a situation where a lot of countries have nuclear weapons, and this increases the chances of a nuclear war happening. This is dangerous for the world, and that is why people are trying to stop nuclear proliferation.