What is 'third person omniscience' in an authors' writing style? How does it characterise the 'voice' an author chooses to write in?
The third person omniscient writing style is when the author is able to speak to all characters' emotions, motivations, beliefs. The author is "all knowing," able to move freely between characters and is not limited. They have the "bird's eye view" of what is happening and are able to write in such a manner. This is where it helps to characterize an author's voice because they are able to possess freedom on what they want to show and how they wish to show it. They are not bound by one character or one voice, but rather can embrace what they want and what they wish to detail. The omniscient aspect allows writers to be able to explore subconscious aspects of motivation, allowing them to purely enter every aspect of a character's understanding, removing as many limitations as possible in the author's telling.
The voice of a literary work can be variable as well as the characters in it. If there is a third person who is omniscient, then the author is saying that the third person is reliable. He is sort of an "infallible" guide in the literary work. However, I would be cautious about the idea of an omniscient person in any literature. You must test whether this person is actually correct. Sometimes the author could have fun with portraying someone as omniscient when in fact he or she is far from it.
If this third person omniscient character is, in deed, reliable, then this character probably represents the author who is, in deed, omniscient, since he or she is the creator of the work.