Short answers, pulled from the story.
Nazi Germany initially maintained a supply of slave labour for homosexuals, criminals, political dissidents, communists, Jews, and the homeless. After the invasion of Poland in 1939, Polish Jews over the age of 12 and Poles over the age of 12 living in the General Government territory became subject to forced labor.
By 1942, all non-Germans living in the General Government were subject to forced labor. This expansion occurred after initial restrictions that started with specific unreliable elements following the invasion of Poland in 1939.
More than 2,000 German companies including Thyssen, Krupp, IG Farben, Bosch, Daimler-Benz, Demag, Henschel, Junkers, Messerschmitt, Siemens, Volkswagen, and Deutsche Bank profited from slave labour. The Organisation Todt was also responsible for engineering projects using conscripted labour and prisoners of war.
Estimates put the number of OST workers between three and 5.5 million who faced extreme mistreatment, severe malnutrition, and abuse. At the peak of the program, forced labourers constituted 20 percent of the German work force and about 15 million men and women were forced labourers at one point during the war.
According to the Potsdam Agreements of 1945, Poles were to receive reparations not from Germany itself but from the Soviet Union's share of those reparations. In 1953 the People's Republic of Poland renounced its right to further claims of reparations from successor states of Nazi Germany.