Here is a link that will teach you everything you need to know about alkalinity. In the referances at the bottom of the page there is more information to give you an even better understanding.
CHEMISTRY AND THE AQUARIUM by RANDY HOLMES-FARLEY
Solving Calcium and Alkalinity Problems
http://www.advancedaquarist.com/issues/nov2002/chem.htm
I find this to be extremely helpful for adjusting my alkalinity as well as calcium and magnesium.
Reef Chemistry Calculator
http://reef.diesyst.com/chemcalc/chemcalc.html