Okay kiddo, so you know how countries sometimes have disagreements and they end up fighting with each other? That's what happened during World War I. Lots of countries were fighting each other, and it was a really big, scary war that lasted for a long time.
Eventually, one side (called the Allies) won the war. They beat the other side (called the Central Powers) and made them agree to stop fighting. That was really important because it meant that the war was over and people could stop fighting and go home.
But it wasn't just a matter of saying "okay, we're done now." They had to make some rules to make sure that everyone would be safe and happy now that the fighting was over. So a bunch of important leaders from the different countries got together and had a big meeting to figure out what to do next.
At this meeting, they came up with something called the Treaty of Versailles. It was a big document that laid out all the rules that the losing countries (Germany, Austria-Hungary, and some others) had to follow. They had to give up a bunch of their land and military power, and pay a lot of money to the winners to help rebuild the countries that had been damaged by the war.
It was a really important moment in history, because it meant that the fighting was finally over and people could start to rebuild their lives. But it was also a really complicated process, with a lot of different opinions and ideas being tossed around. The end of World War I was a big deal, and it changed the world in a lot of ways that we still feel today.