Alkaline refers to a pH abover 7.0. Alkalinity refers to the level of KH.
I suggest you go here Practical Freshwater Chemistry it is a very easily understandible explanation of tank water chemistry and what most keepers should learn. Read both subsections for the above.Note: the term ``alkalinity'' should not be confused with the term ``alkaline''. Alkalinity refers to buffering, while alkaline refers to a solution that is a base (i.e., pH > 7).