Simplify the following text for a Grade 9 native English-speaking person.
Original: In the Democratic People 's Republic of Korea ( North Korea ) , `` Juche '' refers specifically to a political thesis of Kim Il-sung , the Juche Idea , that identifies the Korean masses as the masters of the country 's development .
Simplified: Juche is the group of ideas professed by North Korean leaders Kim Il-Sung and Kim Jong-Il . Juche means self-reliance , and has contributed to North Korea 's isolation .