In third person, the author's voice can be distinct from the characters. But . . . (there's always a but, isn't there?) . . . you must decide what sort of author's voice you want. Do you want an omniscient narrator, who can tell the reader anything you want them to know, like the voice of an old-fashioned storyteller? Or do you want to use what's called third-person limited, in which the narrator provides helpful background information, but generally refrains from telling the reader anything that the viewpoint character doesn't know?
Why would you choose one over the other?
Partly it's a matter of taste. The omniscient narrator gives you more latitude, and when done well can give the reader the feeling of sitting around a campfire, listening to the spinning of a tale. (Tolkien used this voice in The Hobbit.) On the other hand, it takes a fair amount of skill to do well. When done poorly, it gives a feeling that the author was lazy and didn't want to trouble to let the story unfold as the viewpoint character experiences it. I sometimes think of it as the "Attention, K-Mart shoppers!" school of writing, where the author makes pronouncements, rather than letting the reader discover the facts more naturally.
It is the natural unfolding of facts — and the natural suspense, when important facts remain unrevealed — that make the limited narrator such a useful way to tell a story. The author provides descriptions and background as needed, but mostly stays unobtrusively in the background, letting the viewpoint character take the limelight. This way, the reader learns the important facts even as the character does, and feels the tension and frustration of not knowing, when the character doesn't know. It's a powerful way to build suspense, and keep the reader wanting to know more.
