Korea is an East Asian territory that is divided into two distinct and very different countries: North Korea & South Korea. Both sit on the Korean Peninsula.
There are many, many thousands of English teachers working in South Korea. Although they are mainly American, you can find many different nationalities here. In general you’ll need a degree and a good TEFL Certificate to teach in the south.
Read the main article about Teaching English in South Korea.
On the other hand, North Korea is a sworn enemy of the West and incredibly resistant to outside influence. There are extremely limited opportunities for teachers in this quasi-communist state and many stories of foreigners being held there against their will.
Having said this, there are occasionally teaching opportunities here if you like the idea of a challenge!
Read the main article about Teaching English in North Korea.