By following this link, you will discover camps were located all over Europe, including North Africa.
The concentration camp was re-invented by the Nazi's following the internment camps the British set up during the Boer War.
The first, Dachau, was established in 1933, the same year Hitler became Chancellor. It was set up as a work camp to punish those who did not follow Nazi doctrine, were a threat to the regime, were homosexual, religious leaders, or who needed re education.
Buchenwald and other camps were constructed shortly afterwards.
The death camps, Treblinka for example, were constructed simply to kill people. Off the train, into the field, through the forest and into the gas chamber. No real selection process for camp labour or anything else. No chance at life.
The labour camps, Auschwitz/Birkineau for example, were a combination extermination camp and labour camp. Labour from Auschwitz/Birkineau (two camps in the same area within close proximity) supplied labour to the IG Fabren plant, a chemical plant considered necessary for the German War Machine, kept many jews and others alive for a short period before they died from starvation or such diseases as typhoid or dysentery or sent to the gas chambers. Auschwitz as an extermination camp, most arriving on the transport trains, particularly in the later years, went directly from the trains to the gas chamber.
I encourage you to also look at the link Reinhard concerning the extermination camps of Sobibor and Treblinka. A link is also supplied concerning the operations of Auschwitz/Birkineau, it is the last link listed.
I also encourage you to read Night, by Elie Wiesel which is a short book but covers his journey from Hungary to Auschwitz to surviving the death march when the camp was evacuated. It is on Oprah's Book Club.
Mr. Wiesel is one of the most prominant survivors of the Holocaust and well respected by historians. Anything by Martin Gilbert, or Sir Martin Giblert is also very credible. Perhaps these two are the leading experts on the Holocaust.