Bread-Bakers v103.n016.14

Could someone explain the difference between semolina flour and durum 
flour?  I wanted to make the pugliese bread from The Bread Baker's 
Apprentice.  In my small, small town no one sells durum flour.  The King 
Arthur Flour website sells both types of flour and it got me curious as to 
what the difference was, I thought they were the same.  Thanks for the help 
and expertise.  Kudos to Jerry for the detailed information on the unglazed 
tiles.  No wonder we love this list!
Carolyn