Obviously some people are just naturally more gifted when doing certain things. While some people, no matter how hard they work on something, may never get past the amateur level. But passion and hard work can easily tip the scales, and help you find your own talent, your own vision of whatever it is you're trying to do.
I think it's our brain anatomy and chemistry that decides our talents. I don't think this can be changed after you reach full maturity. I believe people are all ''talented'' to some degree. Sometimes it just takes time to find out what you're talented in. A skill that is quick to improve or reaches a very high level tells you that you are talented in that specific field. Of course there are people that are more talented than others and are able hone many skills to a high level. You can see that infants behave very differently from one another even if they haven't learned much already which goes to show how much genetics come into play.
Skills are developed through practise, nature can provide a predisposition to the skill and nurture influences the attitude to the skill. Exceptional talent would be a nurturing of one with the nature to do it. Normal every day talent can be a mix of either.
Everyone has born with a talent, some people just have a hard time finding it, or some people may believe they have no talent, when its right in front of their face, the most obvious talents are sports,arts,and music, yet there are hundreds of other talents out there.