From what I understand, a Super Procedure is similar to an Internal Procedure except it loads into memory and is available to any program at any time - you don't have to have the code in that program to use it. Kinda like running another .p but that .p would be in memory.
While these can be very cool and useful, they can also be hard to debug. I haven't used them yet, but when I do, anytime I make a call to a super procedure I will try to put some comments in the code before the call so when someone else (or myself) has to come back later to figure out what's going on, I know where to look for the code for this super procedure.
Hope that helps!
Rich