Okay kiddo, I will explain what the United Baltic Duchy is in a way that is easy to understand.
A long time ago, there were three countries called Estonia, Latvia, and Lithuania, and they were all part of a big empire called the Russian Empire. But after World War I, the empire fell apart and the three countries became independent.
Some important people thought it would be a good idea to join the three countries together and make a new country, called the United Baltic Duchy. They would have one leader, called a king, and they would all speak the same language, have the same money, and follow the same laws.
But not everyone liked this idea, and some people wanted to keep their countries separate. So the United Baltic Duchy never happened, and Estonia, Latvia, and Lithuania each became their own countries.
Today, they are all independent countries with their own governments, languages, and cultures. But they are still friends, and they work together to make sure they are all safe and happy.