Can someone explain the 'riotous send-up of Korea's society'?

I enjoyed this movie as a straightforward dark comedy. But I keep reading things about how it's a "riotous send-up of Korea's rigidly heirarchical society" (NY Times) and "a political parable about Korean society, a microcosm of Korean social problems" (SubwayCinema).

Not being Korean & having little to no knowledge of Korean society, I feel like I'm missing out on a lot. Can anyone explain in detail how this pokes fun at Korean society? Specific examples please!