Earth is the home planet of humanity. In the setting of the movie, it is apparent that an extensive combination of the world problems of our present (Poverty, Overpopulation, Pollution, Corruption) have been exponentially amplified to create a world where most humans struggle greatly in a messy, unemployed, degraded environment to make ends meet.
Los Angeles, a large city today that is already known for these problems, is the setting of most of the movie on Earth and depicts human life as almost devolved from our time; the buildings are less up to standard, many humans are out of work, and organized crime is substantially rampant and uncontrolled.
It is unknown if a large, catastrophic event (pandemic, post-apocalyptic or nuclear event, government overthrow/mass-anarchy) initiated the deterioration to the conditions we see in the movie, but it is clear that there is still a significantly embedded world economy and industry, as a company like Armadyne is able to successfully profit from security contracts.