Short answers, pulled from the story.
The abbreviation GULAG stands for Glávnoye upravléniye ispravítel'no-trudovýkh lageréy, which translates to Main Directorate of Correctional Labour Camps. This term originally referred only to the division of the Soviet secret police that was in charge of running the forced labor camps from the 1930s to the early 1950s during Joseph Stalin's rule.
After World War II, the number of inmates sharply rose again reaching approximately 2.5 million people by the early 1950s. The system grew rapidly before this period, reaching a population of 100,000 in the 1920s and amounting to 1.5 million by the end of 1940.
A 1993 study of archival Soviet data estimates 1,053,829 people died in the Gulag from 1934 to 1953. The tentative historical consensus is that between 1.6 million and 1.76 million perished as a result of their detention out of 18 million who passed through from 1930 to 1953.
The infamous complexes were those at Kolyma, Norilsk, and Vorkuta all in arctic or subarctic regions. The majority of Gulag camps were positioned in extremely remote areas of northeastern Siberia along Kolyma river and Norilsk near Norilsk with other facilities existing in southeastern parts of Soviet Union mainly in steppes of Kazakhstan.
In the winter of 1941, a quarter of the Gulag's population died of starvation due to harsh working conditions combined with famine caused by the German invasion. This period accounts for about half of all Gulag deaths according to Russian statistics and occurred when Axis armies pushed into Soviet territory from June 1941 on.