I think that gifted and talented are the same thing, just different words.
It is really obvious when a child is talented (gifted) becasue they learn the subject at an abnormally fast rate and show a natural abilty in the subject. I think with singing it is very rare because they need a very fine ear, and a perfect voice....and those 2 do not go together very often. Not many people are talented singers....but many think they are, which really is quite annoyng because they insist on singing.
Talent can be wasted though, and I think this is the saddest thing of all. A talent is like a seed planted inside of someone, and it will only grow so far unless it is helped. A talented pianist is useless if he doesn't have a piano to practice on.
A very good teacher at some point is essential. I had a bad teacher when first started, and stayed with this women for 3 years but somehow had a very natural way of getting around the piano and could move freely and wasn't tense. It was only when I went to a very good teacher that things totally changed and I learnt the meaning of hard work and disipline.
If you look at any great pianist they were all very talented, and worked very very very hard at it. I don't think any of them were just born piansts. I mean of course you had people like Rubinstein who never practiced, but n his book my young years he talks about doing technical work, and practicing long hours. So even if they have a reputation for not practicing now, they would have done when they were a child.
Also....great singers do practce and get a lot of coaching. Where I am, the opera department is by far the busiest department. They get lots of coaching, language classes, acting classes etc....so they work very hard as well.