Alright kiddo, so you know how people speak different languages in different parts of the world, right? Well, a really long time ago, there were people living in a place called the Balkans, which is in Europe. They didn't speak the same languages as people do now, but we can try to learn about what they might have sounded like by looking at old writings and things they left behind.
So, the "paleo" Balkan languages are just the really old languages that people used to speak in the Balkans. Some examples of these languages are Thracian, Illyrian, and Dacian. They were spoken a really long time ago, like before even your great-great-great-grandparents were born!
We don't really know a whole lot about these languages since they're so ancient, but linguists (people who study languages) have tried to figure out what they might have sounded like based on clues left behind. One way they do this is by looking at words that exist in some of the modern-day languages in the Balkans and comparing them to old writings in paleo-Balkan languages.
It's kind of like trying to put together a puzzle with missing pieces. We might not know exactly what the whole picture looked like, but by studying the pieces we do have, we can try to get a better idea of what it might have been like.
So, in summary, paleo-Balkan languages are the really old languages that people used to speak in the Balkans a really long time ago. Even though we don't know a whole lot about them, we can try to learn more by looking at clues left behind and comparing them to modern-day languages.