During World War II, Nazi Germany created many concentration camps, slave labor camps, and extermination camps (death camps). Nazi Germany's leader, Adolf Hitler, thought that certain groups of people were inferior (not as good as others). He even thought there were groups of people who did not deserve to live - he called them "life unworthy of life." These three groups were Jews, Roma people, and people with disabilities. Hitler wanted his Nazis to kill every Jew, Roma, and disabled person in Europe.