Question: what is the difference between informal and formal korean?
Answer: Native Koreans split the system into 존댓말 for "formal" vs 반말 "informal", which in modern South Korean society grammatically really means a mix of 합쇼체 and 해요체 for the first, and 해체 with a little bit of 해라체 for the second. ... It is possible to be informal and yet polite [해요체], or formal and non-polite [해라체].