Extermination camp
The Nazis believed that some groups of people were better than others.  They thought that the Aryan race was the best of all.  They believed that people who were not "Aryan" were "inferior". They also believed that non-Ayrans were the cause of Germany's problems.  They thought that some groups of people did not even deserve to live.  These groups included people with disabilities.  The Nazis called these people Lebensunwertes Leben - "life unworthy of life."