If you want to watch this video, it is very helpful. It's a bit basic, but basic is the best place to start!
http://www.nlm.nih.gov/medlineplus/tutorials/cysticfibrosis/htm/_no_50_no_0.htm
CF is confusing and there's a LOT that is still unknown about it. I've been "exposing" myself to CF info for a long time and am constantly amazed at the complexity of it. Due to the effects that CF has on so many body systems and the dizzying amount of different mutations and gene combo's that there are, I really don't think that all will be known about CF anytime soon, if ever.
I'm sorry. I know it's scary, but humans have a magnificent way of learning to cope with even the most daunting situations, as most of us have on this site. It doesn't make it less scary, but knowledge alleviates some of the anxiety.
Anyway, good luck with your son and good luck with your search for answers.
A. N. Ard