As part of the Nazi system of repression of the population both in Germany and in the occupied countries of Europe, a whole system of pressure, control and killing of opponents of Nazism was developed, which included including Jews, Roma, prisoners of war, communists and other groups who were marked as undesirable by the Nazis. Several types of camp were developed in this system of repression. Concentration camps were places for gathering and imprisoning opponents of Nazism without trial.

Often placed in inhumane conditions, with minimum living standards, they were exposed to long hours of hard physical labor, brutal treatment, torture and humiliation, and as a result of infection and disease, starvation and ill-treatment, many prisoners died. The prisoners in these camps wore striped uniforms and old shoes. Small barracks were built in the camps with wooden beds, often up to four beds on top of each other, and one barrack would house up to 400 prisoners. An estimated 1,000,000 inmates in concentration camps died during the Holocaust.

The concentration camps became a Nazi way of controlling opponents in the period after 1933 in Nazi Germany and throughout Europe from 1938 to 1945. The purpose of the concentration camps was to keep prisoners in one place. The Dachau concentration camp near Munich began operating in 1933, and in 1938, after the annexation of Austria, the Buchenwald and Sachsenhausen concentration camps started operating. The purpose of these camps was to intimidate and eliminate political, social, and cultural movements opposed to the Nazi regime. In the following years other concentration camps were opened, the most famous being the Auschwitz camp.

In many of the concentration camps, the Nazis built or planned to build gas chambers to kill prisoners who were considered weak or sick. Smaller groups of prisoners such as Polish prisoners of the resistance movement, Soviet soldiers and others were also killed in the gas chambers. These chambers were built in the Mathausen, Sachsenhausen, Studhov, Auschwitz 1, Ravensbück and Lublin-Maidanek camps. Medical experiments were also performed on prisoners in many of the camps by the medical staff. Extermination camps (death centers) or death camps are the expression of the sinister plan of the Nazis called the "Final Solution".

The main purpose of these camps, which were in operation from 1941 to 1945, was mass, planned and systematic killing of Jews, Roma and other non-Aryan minorities, and the killing was accelerated to industrial scale that in the period 1943-1944, reaching 6,000 people who were killed on daily basis. In these death camps, people were killed immediately upon arrival. Most of these camps were located on the territory of then occupied Poland by Nazi Germany, and this group of camps included Chelmno 1941-1945, Belzec 1942, Sobibor 1942-1943, Treblinka 1942-1943 , Maidanek 1942-1944, Auschwitz - Birkenau 1941-1945. The oldest camp established in late 1941 was Chelmno for the purpose of killing Jews from the Lodz ghetto.

Upon arrival at the camps, people were first selected, their clothes and personal belongings confiscated, and then directed to the gas chambers, for which were told they are disinfection showers. The victims in the camp were killed with carbon monoxide and were buried in mass graves.

After the Wannsee Conference in January of 1942, the Treblinka, Sobibor and Belzec extermination camps began operating. These camps also had gas chambers in which people were killed by carbon monoxide. The Maidanek camp was put into operation in 1941, and after the Wannsee Conference it became an extermination camp with gas chambers and crematoria. Auschwitz-Birkenau was a complex of camps consisting of a concentration camp, a forced labor camp and an extermination camp. This camp also had more than 40 satellite camps. The deadly gas Cyclone B was used as a method of killing in this camp.

During the Holocaust, more than 3,000,000 people were killed in extermination camps, or about 46% of all Jewish victims during the Holocaust.

The death camps did not exist from the beginning of the Holocaust, but were later developed for a number of reasons: they were the most effective way to kill large numbers of people, they required small number of soldiers to kill huge number of people, the mass killings were known to small number of soldiers and because some of the SS soldiers who were part of the Einsatzgrouppe had serious psychological trauma due to the shootings they had to carry out back then.

Transit camps were a form of concentration camp where people would remain for a brief period of time, as a stopover until their final deportation to the camps. With the expansion of Nazism in Europe and the Nazi conquests, the Nazis in the conquered countries introduced racial and anti-Semitic policies and established a number of transit camps in the occupied countries. Unlike other types of camps, the transit camps were not run by SS units, but by the local Nazi collaborators.

Forced labor camps or so-called Arbeitslager were a form of camp in which "eastern and foreign workers" were brought in and forced to do hard physical labor. These camps were separated from the concentration camps and started operating in 1937. As the need for growth in the Nazi military economy increased, so did the need for free and forced labor, and the invasion of the East opened up the possibility for sending thousands of potential new workers to these types of camps. These camps also had poor sanitation and accommodation, lack of food, medical supplies and clothing, but the prisoners were seen as temporary workers who could always be replaced. By the end of the war, more than 14,000,000 people had passed through these concentration camps for forced labor.

Prisoner-of-war camps were designed to house captured soldiers who opposed the Nazi conquests in Europe. Although Germany was a signatory to the Geneva Convention on Prisoners of War, it did not comply with the conditions set out in the Declaration and provided a minimum standard of living in these camps.