What do plane language and honorific words mean in Korea?

Pinghua is used for people younger or closer to themselves, such as relatives and friends.

Honorific words are used to compare people who are older than themselves or who respect themselves.

Ps When you meet someone older than yourself, but you don't say respectful words, others will think that you don't respect him, so you should ask others' opinions before speaking English (this is for your older people).