Okay kiddo, imagine you have a really big and important house, like a castle. But you don't want just anyone to be able to come inside, right? So you build a special little house right at the entrance to the castle called a guardhouse.
The guardhouse is where the guards stay and keep watch, like superheroes, to make sure only the right people come in. They might ask visitors for a password or ID to make sure they're supposed to be there.
Sometimes there's even a big steel gate that the guards can open and close to let people in or keep them out. Think of it like a super cool fort for the guards to protect the castle!