Okay kiddo, so imagine you and your friend were fighting over a toy, and you both got very angry and upset. But then, you both decide that it's better to stop fighting and make peace instead.
Now, this is kind of similar to what happened with North Korea and South Korea. They used to be enemies and were fighting against each other for a long time, but then they decided to make peace by signing a special document called a "peace treaty."
This peace treaty helped to stop the fighting and made sure that both countries agreed to be peaceful towards each other. It also helped to remove weapons and soldiers from the border between the two countries.
So, just like how making peace with your friend made things better between you two, making a peace treaty helped to make things better between North and South Korea.