when kids ask, I tell them I get sick from the air. it's the easiest explanation. They are asking of course, because I wear a face mask and so it's obvious that there is something different about me. To adults when they ask at work, I tell them I have a genetic lung disease called CF, and it basically makes my lungs produce extra mucus that is a favorite place for bacteria to live, so i get sick easier, so i wear the mask. If they ask more, I tell them more. but usually, no one asks more in depth than that.
My shortest sum up is "It's a genetic disease that can affect the entire body, but the most effected areas are the lungs and digestive system. It causes the body to produce more mucus and that gives way to lung infections, and it also blocks the pancrease from working properly."
When people want more than that, then i go into the salt defect and all that stuff.
Be well.
Ceci