Facts vs. Objects

Wittgenstein says that the world is made up of facts (not objects).  What does this mean?  It might seem particularly confusing, especially since he also says that facts are combinations of objects.  The key to understanding this distinction is to remember that the world has a logical structure.  An object on its own does not have a structure because it is not related to anything else.  But when objects are combined in definite ways (as they are in facts), then the objects are arranged into a logical structure.  Objects are in the world insofar as they are organized into facts.  Objects don't just exist free-floating in the world.  They only exist in the world when combined in definite ways.  The world itself has a logical structure that arranges objects into facts.