Imagine you have a toy gun that can only shoot one foam dart at a time. Now, imagine a toy gun that has three barrels and can shoot three foam darts at the same time. That's a multiple-barrel firearm.
Real multiple-barrel firearms work the same way but with bullets instead of foam darts. They have two or more barrels, which means they can shoot multiple bullets in quick succession. This is useful in situations where you need to shoot many targets quickly, like in a war or if you're hunting a fast-moving animal.
But because multiple-barrel firearms can fire many bullets so quickly, they can be very dangerous if they're not used safely and responsibly. That's why it's important to always follow proper gun safety rules when handling any kind of firearm.