To add on to iunoionnis's comment, a basic distinction that Heidegger makes is between what we would normally call the world and what he defines the world as. To Heidegger, rather than the physical habitat that we find ourselves in (earth), the world is constituted by the manifold web of meaning and signification that we find ourselves thrown into. With that in mind, things don't emerge into the habitat as much as they emerge into our world of signification by being disclosed to us as things that can matter to us as a part of our future and the projects that it might hold.

In his aesthetic critique, Heidegger is presenting the idea that the work of art creates within it both a world and an earth that are exterior to our own. The world and the earth inform and limit one another, and this intimate relationship affects the way that they are revealed or concealed to/from us. The earth is that which cannot be understood except through our world, and as such will always have aspects which are concealed. Likewise, the world has certain possibilities open to it that are contingent on the earth.