Okay kiddo, let me explain what a demilitarized zone (DMZ) is in a way you can understand.
Imagine that you and your friend have a disagreement over a toy you both want to play with. Instead of fighting over it, you both agree to create a space in the middle of the room, where you can both play with the toy without the other person interfering. This space is your demilitarized zone.
In the same way, countries sometimes have disagreements or conflicts, and they may set up a DMZ as a neutral zone to prevent any fighting or military activity in that area. Think of it like a big, invisible line drawn between two countries, and neither side is allowed to cross it with weapons or military forces.
A DMZ can be set up for different reasons. Maybe two countries don't trust each other and want to reduce the chances of an accidental conflict. Or maybe they're in the process of negotiating a peace agreement and need a safe space to talk. Sometimes, the DMZ is monitored by international organizations to make sure both sides are following the rules.
So, a demilitarized zone is like a playground in the middle of the room that you and your friend can share without fighting, but on a much bigger scale between different countries.