Ok kiddo, so you know how a big nuclear power plant makes electricity by heating up water with the heat from nuclear reactions? Well, a micro nuclear reactor is basically a really tiny version of that.
Picture a box that's about as big as a shipping container. Inside the box, there are little nuclear fuel modules that heat up and produce electricity. The whole thing is small enough to fit on the back of a truck or a barge, so it can be transported to places where they need power but can't build a big power plant.
Because the micro reactor is so small, it doesn't need as much safety equipment and can be built with simpler designs. It's also easier to maintain and doesn't produce as much radioactive waste, which is a fancy way of saying yucky stuff that's dangerous to people and the environment.
Some people think that micro nuclear reactors could be a good way to provide power to places like remote villages, military bases, and disaster relief sites. But other people worry that they could still be dangerous and that we should focus on finding other ways to make energy that don't involve nuclear power.
Overall, a micro nuclear reactor is a tiny box that makes electricity by using nuclear reactions. It's smaller and simpler than a big power plant, which makes it easier to move around and use in different places.