Firing port

A firing port is like a small hole on a door that soldiers use to shoot guns out of when they are inside a vehicle or building. Imagine you are playing a game where you have to defend your castle from bad guys trying to get inside. You can build a wall around your castle, but you need to be able to shoot the bad guys if they get too close. However, you don't want to just leave a big door open for the bad guys to walk through. Instead, you can make a small hole in the wall where you can shoot your arrows or throw rocks at the bad guys without making yourself vulnerable. That's what a firing port is like for soldiers. It's a safe way for them to shoot their guns while still being protected.