도시(do-si, dosi)
An area where many people live with developed buildings and facilities
When to use
Large cities like Seoul, Domestic business trips, Talking about city life experiences
The nuance
도시는 is used to refer to densely populated domestic areas with concentrated commercial and cultural facilities.
시골(si-gol, sigol)
Rural areas with fewer people and more nature, unlike cities
When to use
Quiet rural villages, Farming areas, Living environments contrasted with cities
The nuance
시골 is used to denote rural domestic areas with low population and abundant natural environment.
해외(hae-oe, haeoe)
Countries or regions other than one's own country
When to use
Overseas travel, Studying abroad, International trade destinations
The nuance
해외 means foreign countries outside one's own country and is distinct from domestic areas like 도시 or 시골.