Okay kiddo, so have you ever heard of a bomb or a missile? They are big weapons that go boom and can hurt people really bad. But sometimes, if there is a problem with the bomb, it can actually explode by accident. That is very dangerous for the people who are using the bomb or missile, and also for the people who are nearby.
So, some really smart people came up with something called an insensitive munition. This is a special kind of bomb or missile that is designed so that it won't accidentally explode. It is much safer for the people who are using it, and for the people who might be nearby.
The insensitive munition works kind of like a puzzle. When someone wants to use it, they have to do all the steps in the right order, like putting the pieces of a puzzle together. This makes it very hard for the bomb or missile to explode by accident. It only explodes when it is supposed to, and that makes it a lot safer for everyone around.
So, to sum up, an insensitive munition is a special kind of bomb or missile that is designed to be safer for people to use and be around by making it difficult for it to accidentally explode.