Geometric Operations

Hi, long time listener first time caller.
 
Does anybody have any definative info on the geometric data types?
 
for example is there an easy way of returning the x,y co-ords seperatly for the
box type
 
ie select x1,y1,x2,y2 from ..... 
at the moment it looks like I'm going to have to parse out the results to
separate the XY co-ords.
 
Can't find much info at all on the geometric data types at all on the Postgres
site and the doc's are sparse to say the least
 
Any help appreciated
 
Keith