In Korean, the words "Guk" ("gook") and "Tang" both refer to soups. There is always some confusion around this for non-Koreans, and even many Koreans are stumped when asked the difference between the two words. In general, "guk" has more broth and heartier soups served in restaurants are called "tang". In English, there are soups and stews, but in Korean there is also a middle "tang" category between soups ("guk") and stews ("chigae").
Whatever you want to call them, I will always define these Korean soups and stews as yummy.
Seollangtang photo, Naomi Imatome 2010, licensed to About.com.