Third-person omniscient is a viewpoint where the perspective jumps from character to character, showing many points of view over the course of any given scene at once. It generally comes in one of two styles: the omniscient narrator or head-hopping omniscient.
As the name implies, a story told through an omniscient narrator is given through the perspective of a usually-nameless storyteller, someone who is not a character within the story. This narrator is, so far as the story goes, omniscient, with complete knowledge of what all the characters are thinking or doing at any given time. They will often tell the audience what one character is thinking, and then mention what another character is thinking immediately after, rather than restricting what the audience sees to the perspective of one character at a time. Here is an example from the opening of The Lion, the Witch and the Wardrobe by C.S. Lewis:
ONCE there were four children whose names were Peter, Susan, Edmund and Lucy. This story is about something that happened to them when they were sent away from London during the war because of the air-raids. They were sent to the house of an old Professor who lived in the heart of the country, ten miles from the nearest railway station and two miles from the nearest post office. He had no wife and he lived in a very large house with a housekeeper called Mrs Macready and three servants. (Their names were Ivy, Margaret and Betty, but they do not come into the story much.) He himself was a very old man with shaggy white hair which grew over most of his face as well as on his head, and they liked him almost at once; but on the first evening when he came out to meet them at the front door he was so odd-looking that Lucy (who was the youngest) was a little afraid of him, and Edmund (who was the next youngest) wanted to laugh and had to keep on pretending he was blowing his nose to hide it.
As soon as they had said good night to the Professor and gone upstairs on the first night, the boys came into the girls' room and they all talked it over.
"We've fallen on our feet and no mistake," said Peter. "This is going to be perfectly splendid. That old chap will let us do anything we like."
"I think he's an old dear," said Susan.
"Oh, come off it!" said Edmund, who was tired and pretending not to be tired, which always made him bad-tempered. "Don't go on talking like that."
"Like what?" said Susan; "and anyway, it's time you were in bed."
"Trying to talk like Mother," said Edmund. "And who are you to say when I'm to go to bed? Go to bed yourself."
"Hadn't we all better go to bed?" said Lucy. "There's sure to be a row if we're heard talking here."
"No there won't," said Peter. "I tell you this is the sort of house where no one's going to mind what we do. Anyway, they won't hear us. It's about ten minutes' walk from here down to that dining-room, and any amount of stairs and passages in between."
"What's that noise?" said Lucy suddenly. It was a far larger house than she had ever been in before and the thought of all those long passages and rows of doors leading into empty rooms was beginning to make her feel a little creepy.
"It's only a bird, silly," said Edmund.
Notice how over the course of these few paragraphs the narrator first sets the scene without focusing on any specific character, and then how he describes to us the internal thoughts and emotions of both Edmund and Lucy. These are hallmarks of third-person omniscient.
The “head-hopping” variation of the third-person omniscient viewpoint is similar to the third-person limited viewpoint in that it eschews narrators and instead conveys the story directly through the viewpoint of the characters, as though the reader were riding along in the characters’ heads. However, unlike the limited viewpoint, the omniscient viewpoint jumps from perspective to perspective within any given scene—hence the “head-hopping” description. Here is an example from the beginning of Frank Herbert’s Dune:
Paul felt his left hand aching, uncurled the clenched fingers, looked at four bloody marks where fingernails had bitten his palm. He dropped the hand to his side, looked at the old woman. "You did that to my mother once?"
"Ever sift sand through a screen?" she asked.
The tangential slash of her question shocked his mind into a higher awareness: Sand through a screen. He nodded.
"We Bene Gesserit sift people to find the humans."
He lifted his right hand, willing the memory of the pain. "And that's all there is to it—pain?"
"I observed you in pain, lad. Pain's merely the axis of the test. Your mother's told you about our ways of observing. I see the signs of her teaching in you. Our test is crisis and observation."
He heard the confirmation in her voice, said: "It's truth!"
She stared at him. He senses truth! Could he be the one? Could he truly be the one? She extinguished the excitement, reminding herself: "Hope clouds observation."
"You know when people believe what they say," she said.
"I know it."
The harmonics of ability confirmed by repeated test were in his voice. She heard them, said: "Perhaps you are the Kwisatz Haderach. Sit down, little brother, here at my feet."
"I prefer to stand."
"Your mother sat at my feet once."
"I'm not my mother."
"You hate us a little, eh?" She looked toward the door, called out: "Jessica!"
The door flew open and Jessica stood there staring hard-eyed into the room. Hardness melted from her as she saw Paul. She managed a faint smile.
"Jessica, have you ever stopped hating me?" the old woman asked.
"I both love and hate you," Jessica said. "The hate—that's from pains I must never forget. The love—that's...."
"Just the basic fact," the old woman said, but her voice was gentle. "You may come in now, but remain silent. Close that door and mind it that no one interrupts us."
Jessica stepped into the room, closed the door and stood with her back to it. My son lives, she thought. My son lives and is ... human. I knew he was ... but ... he lives. Now, I can go on living. The door felt hard and real against her back. Everything in the room was immediate and pressing against her senses.
My son lives.
Paul looked at his mother. She told the truth. He wanted to getaway alone and think this experience through, but knew he could not leave until he was dismissed. The old woman had gained a power over him. They spoke truth. His mother had undergone this test. There must be terrible purpose in it ... the pain and fear had been terrible. He understood terrible purposes. They drove against all odds. They were their own necessity. Paul felt that he had been infected with terrible purpose. He did not know yet what the terrible purpose was.
Although there is no narrator directing us through the scene, notice how the reader is shown the thoughts of all three characters at various points—the Reverend Mother, Paul, and Jessica.
Advantages and Disadvantages of Third-Person Omniscient Viewpoint
Advantages of the Omniscient Narrator
Easier to write than head-hopping: Since this perspective is very similar to first-person (a narrator relating the story to the readers), it can be somewhat easier to write than the head-hopping style of omniscient.
Tension: Since the author can share with the reader any character’s thoughts or even information that none of the characters know, it is easy to introduce tension through obstacles that the characters don’t know are coming.
Infodumping: Since the narrator can show thoughts from multiple characters and even pause to explain information, it is possible to get across a lot of information in a very short space of time.
Direct address to the reader: As always, a narrator can address the reader directly if necessary.
Advantages of Head-Hopping Omniscient
More immediate than the narrator: Since there’s no one between the reader and the events of the story, the narrative can feel more immediate and real and less like just a story.
Tension: Just as with the narrator, you can convey information from multiple viewpoints or information that none of the characters know.
Infodumping: Again, it is possible to convey information from multiple perspectives very quickly, rather than having to give a separate scene to each perspective.
Most reliable narrator: With its absence of a biased, actual narrator and ability to show the thoughts of many characters in quick succession, this is the single most reliable narration that a writer can provide to a reader.
Disadvantages of Both Types of Third-Person Omniscient
Difficult to write correctly: Third-person omniscient is the most difficult to write without creating viewpoint errors or getting confusing—when you move from head to head, the reader can get lost very quickly and become unsure who is thinking what.
Unfamiliar to many readers: To make matters worse, very few books are written in third-person omniscient these days, so readers are unused to reading it. This means that even if you get it right, readers may still end up confused. This is particularly true with the “head-hopping” variation of omniscient, because to the reader it will often seem like third-person limited until the first time the narrative jumps to another character’s thoughts. This can be very jarring to readers, even if they’ve read omniscient before.
Lack of tension: It can be difficult to keep secrets and tension going if the readers are getting too much information about what is going on.
Infodumping: While it is an advantage that omniscient allows you to convey lots of information more quickly, this is a very difficult thing to do well. Often, this can turn into a firehose-esque flood of information that the reader will be unable to follow.