Okay kiddo, during a big war called World War II, some soldiers from Germany fought against some soldiers from other countries. When the war was over, some German soldiers were captured by the other countries' soldiers and became prisoners of war (or POWs for short).
Now, the northwest part of Europe was where some of the fighting took place, so there were a lot of German soldiers who became POWs there. The other countries' soldiers didn't just let the German POWs go, though. They kept them in special camps where they could make sure the German soldiers wouldn't fight anymore.
In these POW camps, the German soldiers had to stay inside most of the time and follow the rules set by the soldiers guarding them. They usually slept in large groups in bunk beds and ate food that was given to them. Sometimes they were allowed to do things like play games or sports to pass the time.
The other countries' soldiers didn't mistreat the German POWs, but they did want to keep them away from doing any more harm. Eventually, the war ended and the German POWs were allowed to go back to Germany.
It's important to remember that war is not a good thing, and it can have serious consequences for everyone involved. The German POWs were just people caught up in a big and often scary situation.