Konzentrationslager Auschwitz (help·info)) was the largest of Nazi Germany’s concentration camps. Located in German-occupied southern Poland, it took its name from the nearby town of O?wi?cim (Auschwitz in German), situated about 50 kilometers west of Kraków and 286 kilometers from Warsaw. Following the German occupation of Poland in September 1939, O?wi?cim was incorporated into Germany as part of the Katowice District (Regierungsbezirk Kattowitz), or unofficially East Upper Silesia (Ost-Oberschlesien), and renamed Auschwitz. The word Birkenau means ‘Birch tree’ of which there are many surrounding the Birkenau area of the complex.
The complex consisted of three main camps: Auschwitz I, the administrative center; Auschwitz II (Birkenau), an extermination camp or Vernichtungslager; and Auschwitz III (Monowitz), a work camp. There were also around 40 satellite camps, some of them tens of kilometers from the main camps, with prisoner populations ranging from several dozen to several thousand. 
The camp commandant, Rudolf Höss, testifed at the Nuremberg Trials that up to 2.5 million people had died at Auschwitz. The Auschwitz-Birkenau State Museum revised this figure in 1990, and new calculations now place the figure at 1.1–1.6 million,  about 90 percent of them Jews from almost every country in Europe.  Most of the dead were killed in gas chambers using Zyklon B; other deaths were caused by systematic starvation, forced labor, lack of disease control, individual executions, and so-called medical experiments.