I recently saw a meme about fear being something that's not real, though dangers are real. Fear is a very real thing, and so is danger. The two aren't synonomous, nor are they always paired. People fear things that aren't any threat -- and they aren't afraid of many very great dangers, whether through ignorance or naivete or simple denial. Fear is a reaction, emotional and instinctual, to a perceived danger, so that fear really is about perception. Franklin Roosevelt had a point with 'We have nothing to fear but fear itself..." Fear doesn't exist if we don't perceive the danger... And it's very present even if what we fear is no threat; ask anyone who's frozen on stage because they had to speak to a group -- even a receptive group that asked them to be there!
Danger is something that is there, whether we know it, notice it, or care about it. It's an asteroid on collision course with the Earth, that nobody's seen yet. Danger is a predator stalking you, unseen. It becomes a threat, ready to be feared when we come to notice it.
The big thing is how you handle either, and especially both in conjunction. Fears have to be examined, to see if the danger is real -- or you'll be driven by them. Dangers have to be recognized, assessed and prepared for. Fears help us recognize the dangers around us, and our emotional reactions to fear help us prepare physically for a threat. (Which can be a trap for a non-physical danger... but that's another thing to think about...)
The person with no fear is a walking death trap; he doesn't recognize dangers and he doesn't prepare for them. But if the fears go too far, people become immobilized, because they see dangers everywhere. The challenge of life is to balance them both... to control our fears so that we don't get trapped while recognizing dangers, preparing for them.
