Okay, imagine you are playing a game with your friends and you are in charge of a group of people who live in a big area. This area is called a "satrapy" and it's part of a bigger kingdom.
Now, sometimes some of the people in your group might have trouble hearing you or understanding what you want them to do. That's where "aria" comes in. Aria is like a special language that you can use to communicate with those people. It's kind of like using hand signals or body language, but with words instead.
So, when you are in charge of a "satrapy" and need to communicate with your people, you might use "aria" to make sure everyone understands you. It's a really important tool for leaders to use to make sure everyone is on the same page and working together effectively.