An autonomous county is a special area within a bigger country that can control and make its own rules about certain things. It's kind of like a little club inside a bigger club.
Let's say you and your friends all belong to a big club, but you and your best friend really love playing soccer. So you ask the big club if you can make a little soccer club inside the big club. The big club says that's okay, and now you and your friends can make your own rules for your little soccer club, like when and where you play and who gets to be the captain.
An autonomous county is like your little soccer club. It's still part of the big country, but it gets to make its own rules based on what the people there want and need. For example, maybe they speak a different language or have a different culture, so they can make rules that help protect and celebrate that culture.
But even though they have some control, they still have to obey the big country's overall laws and rules. Just like how your little soccer club still has to follow the big club's rules about respecting others and sharing the field with other groups.
So basically, an autonomous county is a special little area within a bigger country that gets to make some of its own rules, while still following the bigger country's rules.