Here are some quotes from the Arolsen Archives web site:
“After the Second World War, the Allied occupying powers were faced with a mammoth task: they wanted to document the crimes committed by the National Socialists and search for missing persons. In order to do so, they collected information about the victims of Nazi persecution. In the American Zone of Occupation alone, this resulted in the creation of around 850,000 documents containing information on ten million names. The Arolsen Archives have now put this collection of documents online.”
“To make sure the new information can be accessed quickly and easily, the Arolsen Archives enlisted the support of Ancestry, the largest online platform for genealogical research. This year the company began helping to process large collections, making the data available to the Arolsen Archives as well as publishing the documents in its own online archive. Because of this, the lists can now be searched very easily. ‘The data collected by Ancestry enrich our online archive with a lot of valuable information, including information on the whereabouts of foreign forced laborers, for example,’ explains Giora Zwilling, Head of Archival Description at the Arolsen Archives.”
The archive obviously documents millions of people who perished during the Nazi persecutions. However, not everyone listed in the archives died. You can also find the stories of many who suffered but survived.
You can read more and also search the Arolsen Archives by starting at: https://arolsen-archives.org/.