Say you're starting to get peckish. Dinners not for another couple or few hours, and you don't want to spoil it by eating a lot. But hunger will distract you from anything else you're doing if you don't eat something.
Peanuts sometimes work. I tend to have a jar of roasted peanuts lying around. But peanut butter seems to be more efficient. Today one spoonful did the trick. Granted, it was a pretty big spoon.