Difference between AX 2009 and AX 2012

Hello,

I'm new to AX world. Can someone help me to know the difference between AX 2009 and AX 2012 functionality wise. I tried to search on it and I'm able to see information related to Technical side but not on Functional side.

I would like to know the major differences between these to versions, specially in Functional aspect.Please do share me if you guys have any documents or links to know more about these.

Thanks,

Ganesh B