What is the boy in the striped pajamas about

The boy in the striped pajamas is a movie about a family moving in a new house near a concentration camp in Nazi Germany. The young son in the German family goes exploring and finds the edge of the camp and befriends a Jewish boy. They talk and try to understand why they are where they are there (meaning why is each boy on different sides of the fence). As time goes by, the son starts to learn about the Jews and why they are locked away from his homeschooling teacher, his sister, his father, and his mother. The mother learns that the Jews are being burned and is mortified of the father who happens to be a ranking official. As the boys get along more, the German boy decides to go into the camp to see what is is like for the Jewish boy. So together, they experience the camp until the guards pick out some prisoners (the two boys included) and they take the prisoners into a series of rooms to undress, shower, and eat. By this time, the German boy's family notices that he is missing and follows his trail to the edge of the fence.The guards put all of the prisoners into a room, and close the only door. Gas is poured in and the prisoners (plus the German boy) are killed. The German boy's family didn't get to him soon enough.

The meaning of the word in this sentence is unneeded