I just recently found out that some axes are for chopping down trees and others are for splitting firewood.
I hear Fiskar axes are great for splitting wood. 
Yes they are, my boyfriend just bought me my first very own brand new axe last month. I am not sure what the difference is between the splitting and chopping down axe though.
The design of the axe is the largest difference. They design the head and handles for what they are intended to cut. 
I am looking at my new Fiskars axe and the blade head is thin then gets wider quickly which I assume helps the wood split. I wonder what the handle difference would be, length maybe?
The longer the handle is the more momentum and control can be used.