Hitler's most cherished dream was to create an exclusive racial community of pure Germans. So the moment he came into power, he began to implement his dream. He wanted to physically eliminate all those who were seen as `undesirable' in extended empire Nazis wanted only a society of 'pure and healthy Nordic Aryans'. 

They alone were considered 'desirable'. Only they were seen as worthy of prospering and multiplying against all others who were classed as 'undersirable'. This meant that even those Germans who were seen as impure or abnormal had no right to exist.
Alongwith Jews, gypsies and blacks were also living in Nazi Germany. They all were classified as 'undesirable'. 

They were viewed as racial 'inferiors' who threatened the biological purity of the 'Superior Aryan' race. Hence, they were widely persecuted. Even Russians and Poles were considered subhuman. When Germany occupied Poland and parts of Russia, captured civilians were forced to work as slave labour.

However, Jews remained the worst target of Hitler. They lived in separately marked areas called Ghettos. They were often persecuted through periodoc organised violence, and expulsion from the land. Hitler was not satisfied with this only. 
He wanted total elimination of the Jews. From 1933 to 1938 the Nazis terrorised, pauperised and segragated the Jews, compelling them to leave the country. 

The next phase, 1939-1945, aimed at concentrating them in certain areas and eventually killing them in gas chambers in Poland.
Polish children who looked like Aryans were forcibly snatched from their mothers and examined by 'race experts'. If they passed the race tests they were raised in German families and if not, they were deposited in orphanages where most perished.