Okay kiddo, I'll explain it to you like you're five! So, you know how Poland is a country, right? And other countries like Germany and Ukraine are next to it. Well, when people want to go from Poland to those other countries, sometimes they have to cross a special place called a border.
A border is like a big line that separates one country from another. And when people cross that line, they have to show some special papers to the people who work there. Those people are called border guards.
Now, let's talk specifically about the border crossings for trains. Trains are big vehicles with lots of people on them that can travel long distances. To cross the border by train, the train has to stop at a special border station. This station is where the border guards check everyone's papers to make sure they are allowed to enter the new country.
Sometimes there are special rules about what you can bring with you from one country to another. For example, if you're going from Poland to Germany, you might not be able to bring certain types of food or animals with you. The border guards will tell you about these rules so you don't get in trouble.
Once the border guards have checked everyone's papers and made sure everything is okay, the train can continue on its way to the new country. It's important to follow the rules and show the right papers when you're crossing a border, otherwise you might not be allowed to go where you want to go.
Does that make sense, kiddo?