The CPA site im with says i need a sub id to track converstions. Can anyone explain to me what it is and how i can make one?

you should ask am how you can setup those on your network. but should be something you add into end of url.

sub id is for tracking different promotion methods for example

http://link/offer.php?subid=id1
http://link/offer.php?subid=id2

you put your link that one with id1 everytime someone clicks that you see it on your stats as id1 , when someone clicks the link with id2 it will show it in stats so you can see how many clicks and conversions you got from different places for same offer. Otherwise you can't know from which link the visitor came.

It's extra data to help analyze your stats. You can indicate traffic source, PPC keyword, etc. Usually it's appended to the end of your tracking link in the manner &sub1=mysubidinfo but ask your AM before setting one up.