Can you explain the nier automata back story?

Well, the Nier Automata back story is complex. Long ago, there was a great calamity that almost wiped out humanity. The aliens invaded, and in response, humans created androids. But things didn't go as planned. The androids have to fight the machines that the aliens left behind on Earth. The story also delves into the nature of the androids themselves, like 2B and 9S, their relationships, and how they come to terms with their existence in this war - torn world. It's a story about survival, identity, and the struggle between different forms of life.

The back story of Nier Automata is set in a post - apocalyptic world. It involves a war between machines created by aliens and the remaining humans and their android defenders. The androids are sent to reclaim Earth from the machines. There was an earlier conflict that led to the destruction of much of the world as we know it, and the androids are now humanity's last hope in this desolate setting.