Snow Piercer movie takes place after the destruction of the world. The world is covered by ice and snow, it’s a new ice age.
Korean director Joon-ho describes Snow Piercer as a post-apocalyptic movie and is about a few survivors who end up on a train together (where it's going, he don't know?). It's set after the "apocalypse" has already occured and the whole world is in shit street covered by ice and snow, "some kind of new ice age." The train wiill include survivors from all over the world and it is divided by economic classes, so the people are fighting each other over that class struggle thing.
Apparently it will be a bit different from the actual printed graphic novel that the movie will be based on (so it's not a direct adaptation), but it's still about examining the human condition and whatever else that all entails.