Short answers, pulled from the story.
Kliment Voroshilov was one of the original five Marshals of the Soviet Union and a close ally of Joseph Stalin. He served as People's Commissar for Defence, commanded Soviet forces in the Winter War and at Leningrad during World War II, and later served as Chairman of the Presidium of the Supreme Soviet, the nominal head of state, from 1953 to 1960.
Voroshilov first met Stalin in April 1906 in Stockholm, where they shared a room while attending the Fourth Congress of the Russian Social Democratic Labour Party. Their friendship deepened at Tsaritsyn in 1918, where they jointly led the Red Army's defense of the city.
Voroshilov commanded Soviet forces during the Winter War from November 1939 to January 1940, during which the Red Army suffered roughly 320,000 casualties compared to about 70,000 Finnish casualties. Stalin blamed him for the failure, and Voroshilov was subsequently replaced as Defense Commissar by Semyon Timoshenko.
Voroshilov personally signed 185 documented execution lists during Stalin's Great Purge of the 1930s, placing him fourth among the Soviet leadership after Molotov, Stalin, and Kaganovich.
On the 15th of March 1953, Voroshilov was approved as Chairman of the Presidium of the Supreme Soviet, making him the nominal Soviet head of state. In that capacity he presided over death penalty appeal reviews, where researchers found he frequently pushed toward leniency for repentant prisoners and those convicted of crimes of passion.
Voroshilov married Ekaterina Voroshilova, born Golda Gorbman, a Ukrainian Jew from Mardarovka who converted to Orthodox Christianity to permit the marriage. They met while both were in exile in Arkhangelsk, where Ekaterina had been sent in 1906.