Imagine you and your friends like to play a game where you pretend to be soldiers. A "kill house" is a special place where you can practice being a soldier safely. It's like a big house with lots of rooms that are set up like a battlefield. You can run through the rooms and practice things like shooting fake guns, figuring out how to get through doors quietly, and working together with your friends. It's not a real battle, so nobody gets hurt, but it helps you get better at pretending to be a soldier.