What's the difference between South Korea and North Korea?

I've answered this question several times so I'm just going to quote wiki: The division of Korea into North Korea and South Korea stems from the 1945 Allied victory in World War II, ending Japan's 35-year colonial rule of Korea. In a proposal opposed by nearly all Koreans, the United States and the Soviet Union agreed to temporarily occupy the country as a trusteeship with the zone of control demarcated along the 38th parallel. The purpose of this trusteeship was to establish a Korean provisional government which would become "free and independent in due course." Though elections were scheduled, the Soviet Union refused to cooperate with United Nations plans to hold general and free elections in the two Koreas, and as a result, a Communist state was permanently established under Soviet auspices in the north and a pro-Western state was set up in the south. The two superpowers backed different leaders and two states were effectively established, each of which claimed sovereignty over the whole Korean peninsula. The Korean War (1950–53) left the two Koreas separated by the Korean Demilitarized Zone through the Cold War to the present day. North Korea is a communist state — though the last instances of the word Communism were removed from its constitution in 2009 — often described as Stalinist and isolationist. Its economy initially enjoyed substantial growth but collapsed in the 1990s, unlike that of its Communist neighbor People's Republic of China. South Korea emerged, after decades of authoritarian rule, as a capitalist liberal democracy. Since the 1990s, with progressively liberal South Korean administrations, as well as the death of North Korean founder Kim Il-sung, the two sides have taken small, symbolic steps towards a possible Korean reunification.

Actually, the language (dialect) is somewhat different. As to why they are separated, that happened in 1945 after the end of WW2 and the occupation by Japan. The war (which is still going) was actually started by North Korea in an attempt to reunite the country. It was/is NOT a war between China and the US. It caused a UN police action that the US, along with many other countries was/is involved in. The conflict is currently in a stalemate cease fire and could re-ignite at any time.

I think the 38th parallel. Just kidding. The Chinese in the north and the Americans to the east both wanted to test their current military strength. Korea was a good place to do it because it because it wasn't in either country.

Three words: Kim Jung Il