Short answers, pulled from the story.
Kim Il Sung was a North Korean revolutionary, military officer, and dictator who founded the Democratic People's Republic of Korea in 1948 and led it until his death on the 8th of July 1994. He was in office for more than 45 years, making him the third-longest serving non-royal head of state and government in the 20th century.
Kim Il Sung was installed by the Soviet Union following Japan's defeat in World War II. Soviet General Grigory Mekler's positive assessment of Kim led senior Soviet officials, including Lavrentiy Beria, to recommend him to Stalin. In December 1945, he was installed as first secretary of the North Korean Branch Bureau of the Communist Party of Korea, and became premier when the Democratic People's Republic of Korea was proclaimed in 1948.
Juche was Kim Il Sung's political ideology, originally described as a variant of Marxism-Leninism, focused on the principles of independence, self-sustenance, and self-defence, combined with Korean nationalism. It was developed in opposition to the idea of North Korea as a satellite state of either China or the Soviet Union, and was formally promoted as state ideology from October 1966 onward.
Songbun was a caste system Kim Il Sung introduced on the 30th of May 1957, dividing the North Korean population into three classes: core, wavering, and hostile. Classification was based on political, social, and economic background, and determined access to education, housing, employment, food rationing, party membership, and even where a person was allowed to live. The system persists in North Korea today.
Kim Il Sung collapsed from a heart attack on the 7th of July 1994 at his residence in Hyangsan, North Pyongan, and died in the early hours of the 8th of July 1994, aged 82. His death was not announced for 34 hours. A ten-day mourning period was declared, and his body was placed in the Kumsusan Palace of the Sun, where it remains on public display. A 1998 constitutional amendment named him Eternal President of North Korea.
The Korean War began in 1950 when North Korean forces invaded South Korea. Archival material indicates the decision to invade was Kim's initiative. The conflict drew in United Nations forces led by the United States in defense of South Korea, and later Chinese troops in support of North Korea. A ceasefire was signed on the 27th of July 1953 after more than 2.5 million people died, leaving Korea divided along what became the permanent Military Demarcation Line.