Okay kiddo, so an anti-tank gun is a special kind of weapon that is used to destroy big and tough vehicles called tanks. These tanks can be really dangerous because they have thick armor to protect them, but the anti-tank gun is a weapon that can pierce right through that armor.
It looks kind of like a big tube that is attached to a stand. The tube is filled with explosives and there's a trigger that sets off the explosion when the gun is aimed at a tank. When the gun fires, a powerful explosion happens and a bullet-like projectile is shot out of the tube really fast.
The bullet is designed to pierce through the tank's armor and cause a lot of damage to the inside of the tank. This is important because if the tank is damaged enough, it won't be able to move or shoot anymore, which makes it a lot easier to defeat in battle.
Anti-tank guns are used by soldiers who are trained to operate them, and they are usually set up in places where tanks are expected to pass through, like on a battlefield or at a checkpoint. They can also be mounted on vehicles or carried by soldiers on foot.
So basically, an anti-tank gun is a special weapon that helps soldiers destroy big and tough tanks so they can win battles and stay safe.