Short answers, pulled from the story.
The Gulag was a system of forced labor camps in the Soviet Union. The word GULAG originally named only the secret police division that ran the camps, standing for the Main Directorate of Correctional Labour Camps. In English it came to mean the whole Soviet system of prison-based unfree labor.
The tentative historical consensus holds that of the 18 million people who passed through the Gulag from 1930 to 1953, between 1.6 million and 1.76 million died as a result of their detention. About half of all Gulag deaths occurred between 1941 and 1943 following the German invasion. A 1993 archival study estimated 1,053,829 deaths from 1934 to 1953.
The Gulag was officially established on the 25th of April 1930 by an OGPU order. It was formally abolished on the 25th of January 1960, when its administration was dissolved under Khrushchev. Forced labor colonies continued afterward, and political prisoners were held at Perm-36 until 1987.
Aleksandr Solzhenitsyn wrote The Gulag Archipelago, published in 1973. He had survived eight years of Gulag incarceration and won the Nobel Prize in Literature. He likened the scattered camps to a chain of islands and described the Gulag as a system where people were worked to death.
Stalin expanded the Gulag alongside collectivization and rapid industrial development beginning around 1929. The camps were meant to colonise remote regions and to provide cheap forced labor for mining and construction in the east and north. The system became an independent branch of the national economy, though it was never actually profitable.
Most Gulag camps stood in extremely remote areas of northeastern Siberia, such as the Kolyma region and Norilsk, and in the steppes of Kazakhstan. Towns including Karaganda, Norilsk, Vorkuta, and Magadan originated as blocks of camps built by prisoners. Russian historians have described 476 separate camp administrations across the USSR.