Question: [The Wikipedia article on Korea](https://en.wikipedia.org/wiki/Korea) states that South Koreans call Korea 한국, while north Koreans call it 조선. Do 'Korea', '한국', and '조선' all refer to the same thing? If so, how did the three different names come about?

Answer: 
Usually, 'Korea' and '한국' refer to South Korea(Republic of Korea, 대한민국), and '조선' indicates North Korea(Democratic People's Republic of Korea, 조선민주주의인민공화국).
'Joseon(조선)' is a country that has been destroyed and does not exist at present. In a modern society divided into South and North Korea(북한), there is only North Korea that calls itself Joseon. The official name of Korea (남한, South Korea) is Republic of Korea.