It is one of the most powerful tools in the writer's toolbox. Victor Hugo used it. So did Jane Austen, Ernest Hemingway, and Robert A. Heinlein. In fact, it used to be the tool of choice for many great writers, but today it has fallen out of favor. You are probably already familiar with the term.
Omniscient narrator is that mode of writing where the story is told in the author's voice.
It gives the author godlike flexibility, allowing him or her to dip into the thoughts of any character at any time. There are no restrictions on how information is delivered to the reader. Well, nowadays, editors consider omniscient narrator yesterday's music. Just like Britney Spears, character-driven stories are all the rage. If you start the scene in Character A's head, you must stay in Character A's head until the scene is over.