There are things that will naturally interfere with GPS and they are fairly well known. The FAA provides an expected outage map [1] (a forecast, if you will) for pilots that may need that info. Jamming is an act by humans to intentionally disrupt the GPS signal.
Could be. I was directly answering "what's the difference?"
It's hard to know intentionality without also knowing where there is expected+natural interference. Of course, when a region is surrounded by persistent GNSS issues and is a known war-zone with large actors, intentionality is fairly reasonably assumed.