Imagine you have a secret that you want to tell your best friend, but you don't want anyone else to find out. That's a bit like how the government has secrets too, but they need to keep them safe from people who shouldn't see them.
Controlled unclassified information (CUI) is a way the government organizes and protects information. It's information that's not a top secret, but it's still important and needs to be kept safe from people who don't have permission to see it.
Think of it like a fancy folder that has a lock on it. Only certain people who have the right key can open the folder and see what's inside. That's how the government protects their important information from getting into the wrong hands.
CUI can include things like financial records, scientific research, or sensitive personal information. By keeping it protected, the government can make sure that only the right people have access to it and it doesn't fall into the wrong hands.