Grilling or smoking, im really lost on this?

i have a smoker which i use to grill by putting the lowest rack close to the charcoal pan. but i dont understand the whole idea about smoking, i know it adds flavor from the smoke of wood. but i also know meat is supposed to be cooked to certain temperatures to be safe. i have even heard the term cold smoking where the meat doesnt reach anywhere close to cooking temperatures. is the meat supposed to be smoked first and then cooked to proper temperature or cooked and then smoked. i make my own jerky in a dehydrator that only gets up to 130 degrees which is under the proper cooking temperature for beef. ive never gotten ill. is it the salt in the cure? does meat in a smoker have to have a salt cure first? i am also curious about pre packaged beef jerky, how can it sit un refridgerated for a few years and still be safe to eat.