Okay kiddo, gun laying is when you try to aim a gun at something far away. Imagine you're playing with a water gun and you want to squirt a target that's really far away. You can't just point and shoot, you have to adjust your aim.
Now, real guns are much bigger and more powerful than water guns, so it's a lot harder to aim them. That's where gun laying comes in. The people who operate big guns use special instruments to help them aim. These instruments tell them how high and low to aim, and how far to adjust the gun to the left or right.
But wait, there's more! Sometimes the ground isn't level, or there's wind blowing, or the target is moving. All of these things can make it even harder to aim the gun. That's why gun laying involves a lot of math and physics. People who know a lot about those things use special formulas and calculations to help the gun operators aim more accurately.
So, gun laying is all about aiming a big gun with special instruments and using math to make sure you're aiming at the right spot. It's kind of like playing a very complex game of water gun target practice!