Ok kiddo, do you know that sometimes people do very bad things and they have to pay for those things they did wrong? Well, after the Second World War, some people in Germany did such really bad things that it was important to make sure they paid for those things, so some other important people from different countries came together to have a big meeting in a city called Nuremberg.
This big meeting was called the Nuremberg Trials, and it was like a big court for the people who did very bad things, you know like stealing and hurting other people, but on a very very big scale. These bad people were called war criminals and they did things like hurting and killing many many people because they didn't like people who were like them.
So these important people from different countries got together in Nuremberg and decided that they needed to punish the war criminals for all those bad things they did. They talked and talked for many days and finally came up with some rules for the war criminals to follow.
They said that the war criminals had to come to court and tell the truth about what they did wrong. That means that they had to tell everything about how they hurt and killed many people, and why they did it, even if it means they might go to jail.
So the war criminals came to court, and people stood up and asked them many many questions about what they did wrong. They talked about all the bad things that happened during the war and how the war criminals were responsible for them. After all the talking and questions, the judges made a decision on what to do with the war criminals.
In the end, they decided that some of the war criminals should go to jail for a very long time, and others should be punished in other ways. This was to help show people that doing bad things, especially really really bad things, can get you in trouble and that it's important to always do good things and be kind to others.