So, South Korea is a big country with lots of cities, but there are some special cities that are different than the others. These special cities are called "metropolitan cities" and there are six of them: Seoul, Busan, Daegu, Incheon, Gwangju, and Daejeon.
What makes these cities special is that they are big cities with lots of people living in them and lots of important things happening there. They are like the "capital cities" of different areas in South Korea.
For example, Seoul is the capital city of South Korea and has lots of important buildings, like the Blue House where the president lives, and big companies like Samsung and LG. Busan is a big port city that is very important for trade and shipping, while Incheon is a city near the airport where lots of people come and go from the country.
These special cities also have their own local governments that are in charge of making decisions for that area. So, just like how your town might have a mayor and city council, these special cities have their own leaders who make decisions for the people who live there.
Even though these special cities are different from the other cities in South Korea, they are all important and work together to make the country a great place to live.