The textbook I recommended above goes into this in much more detail, but I'll try to give a brief intro.
The currently dominant map for understanding brain structure is the Brodmann map ; it's largely anatomical (clusters of densely interlinked neurons with mappable connections to others. The visual cortex is composed of brodmann areas 17 (primary visual cortex, containing a more-or-less bitmapped visual field), 18 (secondary visual cortex), and 19 (Third visual cortex). The visual cortex is divided into two streams, a ventral stream used to identify and characterise objects, and a dorsal stream used to locate those objects in a strategic way. This is known as the "two streams hypothesis" (in case you want to look it up).
I could go a bit further, but I'm not sure how long slashdot's max comment length is and a textbook would probably give you a better understanding than what I can give you off the top of my head.