Partner NOC: Allows you to sell internal cPanel licenses. Essentially, you can sell cPanel licenses to people who are purchasing hosting from you. As of right now you need 35 licenses to qualify to become a Partner NOC and this will be changing in the coming weeks.
Distributor: Allows you to sell external cPanel licenses. You are able to sell cPanel licenses to anyone, not just those purchasing hosting from you. However, you must first become a Partner NOC before even being considered to become a distributor. It's best to think of Partner NOC as your "foot in the door" to prove yourself worthy of becoming a Distributor.
If you are serious about becoming a cPanel Partner NOC, I recommend you e-mail [email protected] to start the process.