Okay, kiddo, so a castellan is like the boss of a castle. You know how a castle is a big old building with walls and towers and stuff? Well, back in the olden days, castles were very important places because they were where rich and powerful people lived to keep themselves safe from enemies.
Anyway, the castellan is in charge of making sure everything in the castle is running smoothly. They are responsible for making sure there is enough food, water, and other supplies for the people who live there. They also have to make sure the castle is safe from attackers, so they might organize soldiers to help protect it.
The castellan also manages the people who work in the castle, like the cooks, cleaners, and guards. They make sure everyone is doing their job properly and that the castle is kept clean and tidy.
In a way, the castellan is kind of like a king or queen of the castle because they are in charge of everything that goes on inside of it. But they have to work hard to make sure everyone is happy and safe.