The 2 hole in the 1. power outlet is the place where the plug is connected to the power plug, the same as in France, Germany, Australia, Greece, and Turkey.
2. the voltage of South Korea is 220V, but the frequency is 60Hz, which is 10Hz higher than that of China. The general Chinese electric appliance can be used directly in Korea. If your electrical appliance does not match the other voltage specifications or plugs, and you do not prepare the transformer or switch the plug, you can borrow it from the hotel service desk. Transformers or switching plugs can also be purchased in duty-free shops, convenience stores in Inchon airport or Longshan electronic business street.