Extermination camps were facilities established during World War II primarily by Nazi Germany for the industrialized mass murder of millions, primarily targeting Jews in the Holocaust, along with other persecuted groups such as Romani people, Soviet POWs, and others deemed undesirable by the Nazi regime. These camps functioned as part of the 'Final Solution,' where victims were systematically killed in gas chambers and through other cruel methods, often being misled about their fate until the very end.