Often, the question arises...
What is the difference between a KZ, and a KL? Or a KL and AL perhaps..? Below is a brief explanation. Remember, throughout the tens of thousands of camps and prisons utilised by the Nazis throughout the Third Reich period, approximately fifty different classifications were introduced. The German love for putting everything and indeed everybody in the right place, was no more evident than with this categorisation. Here is a brief list of some of the more common terms and abbreviations...
KL and KZ = Konzentrationslager (Concentration Camp) basically, both the same. KZ was used as it sounded harder. A KL could have a large complement of subordinate camps, even topping the century mark.
NL = Nebenlager (Subcamp).
AL = Aussenlager (External Camp). Technically, could still be subcamps, as under the administration of a Stammlager (Main Camp).
Arbeiterziehungslager = Worker Education Camp
Arbeitslager = Labour Camp
Durchgangslager = Transit Camp
Internierungslager = Internment Camp
Sammellager = Assembly Camp
Straflager = Punitive Camp
Straflager für Arbeitsverweigerer = Penal Camp for Persons Refusing to Work
Vernichtungslager = Extermination Camp. Sometimes referred to as Todeslager (Death Camp).
Wohnlager = Residence Camp
Zwangslager = Forcible Detention Camp
Zwangsarbeitslager = Penal Servitude Camp
Note that many camps fell under more than one category. For example, KL-Auschwitz was both a Vernichtungslager (extermination camp), and Arbeitslager (work camp). KL-Holleischen, also referred to as Aussenarbeitslager-Holleischen, was an external subcamp of KL-Flossenbürg, yet an Aussenlager (external camp) supplying work for MWH (MetalwerkeHolleischen) munitions facility, whilst also served as a Ausbildungslager, i.e. training camp for SS-Aufseherinnen (female guard staff) for the subcamps of KL-Flossenbürg.
Generally speaking, Konzentrationslagers were divided into four categories during the 1940-1941 period. Note that extermination camps would not fit into this categorisation, due to the period.
Categories I and Ia - Work camps such as KL-Dachau.
Category II - Harder labour and living conditions locales, such as KL-Buchenwald.
Category III - KL-Mauthausen. Reserved for prisoners considered as serious offenders.
p.s. Some of the above terminology may well have been created post war, to enable clarification for various reasons. This list, compiled from numerous sources over a lengthy period, was created as a reference and should not be treated as a sole historical source.