Okay kiddo, so you know how different countries have cities with their own governments and laws, right? Well, back in the olden days, there were some cities in Germany that didn't belong to any one king or ruler. Instead, they were called "imperial free cities," which meant they were kind of like mini-countries all on their own.
These cities were pretty special, because they had a lot of freedom to govern themselves and make their own rules, without having to answer to anyone else. They were also allowed to handle their own trade and money, which made them pretty important places for business and commerce.
But being an imperial free city wasn't always easy. Sometimes, other rulers would try to take over these cities or force them to join their kingdom. And sometimes, the people living in the city would disagree about what rules or laws they wanted to have. But despite these challenges, these cities managed to survive for centuries and help shape the history of Germany.
So basically, an imperial free city was like a really cool city-state that got to make its own rules and run its own show. And even though it wasn't always easy, it was a pretty unique and important part of German history.