Concentration Camps are the camps what the Nazi's put the Jews in. Most of the camps such as Auschwitz, Belzec, Chelmno, Majdanek, Sobibor, Treblinka, and Mauthausen were located in Poland. The first camp ever made was Dachau. It was built because the Nazi's didn't have anywhere to put the Jews from the Ghettos. Jews and any other people who the Nazi's thought were "undesirable", such as homosexuals, Jehovah's Witnesses, etc. were put in these camps because it was a plan Germany had.
Germany's Plan was called Final Solution. This was the plan to kill all of the Jews. Hitler discusses his plan in his book Mein Kampf, which he wrote in prison before World War II. Hitler says that they are evil and he wanted world domination. Hitler shows in this book that he thought Jews were a race that wanted world dominance.
The so-called world dominant Jews were classified Jews by their grandparents. Anyone with three Jewish grandparents was A Jew or anyone that had two Jewish grandparents and was part of a synagogue on September 15, 1935 was considered a Jew. Also anyone with any Jewish blood at all was a Mischlinge. They couldn't do very much in the German community but they were freer than the Jews. The Mischlinges could be in the army but they could not be officers or any higher rank. The very First Action the Nazi's took was that Jews were not allowed them to go to German schools. Those rules also said the Non-Aryans could not work at certain places or do thing the other German's could do.
Himmler was one of the people who helped Hitler establish those rules. Hitler had chosen him to be in charge of the SS, which went with the army and rounded up Jews and other people. Himmler used to also be Hitler's bodyguard so he had a big influence on Hitler. Himmler was the man who took all of the Jews to the concentration camps.
The Concentration Camps that Himmler went to were very bad. The Jews were transported there in tightly packed railroad cars without food and water. Right when the prisoners got off the train they would go right to work. Some of the prisoners wouldn't get out of the train and they were threatened and then shot. The concentration camps were built along railroads for easy access. Right when they entered the camps they would get examined by the doctor's on site. If the prisoners weren't strong they would be sent to the left, which meant death right away. If the doctor pointed to the right the prisoner would enter the concentration camp.
When the prisoners got into the camp the Jewish Guards (Kapos) would make them obey Nazi orders, so they could be favored by the Nazi's. These Kapos would act like the German Guards and make them do what the Nazi's said. This made it very hard to survive in these death camps. There was never a working bathroom inside the camps and they German Guards wouldn't be the prisoners regularly. "The sanitary conditions were indescribable. There was one bathroom, always out of order, for a hut of four hundred people" as one person describes from the Eichmann trail. The sanitary conditions were terrible but the camps also carry many diseases. Typhus was common with the prisoners and so was malnutrition. If people were sick they would pretend not to be so they wouldn't get beaten.