Dominium maris baltici

Dominium maris baltici is a big fancy word that means control over the Baltic Sea. Imagine you live in a big house with a swimming pool in the back yard. You and your family love to swim and play in the pool. You're in charge of the pool because it's in your yard and you control who gets to swim in it.

Now imagine that the Baltic Sea is like a really big pool that many different countries want to use. Dominium maris baltici is saying that one country (or group of countries) should get to control who gets to use the Baltic Sea and be in charge of it, just like how you're in charge of your pool.

Some countries (like Sweden and Denmark) in the past have argued that they should be in charge of the Baltic Sea because they are close to it and have been there for a long time. Other countries (like Germany and Russia) have wanted control over it too.

Nowadays, different countries have different ideas about who should be in charge of the Baltic Sea, and it's a complicated issue. There are different agreements and organizations that help countries work together and share the Baltic Sea, but no one country has complete control over it.