Effaced Narration/Narrator - what is it?

So, this is a narrator that "knows what is available". Neutral camera is a good way to think of it. Lots of external description, action description, etc, from the narrator. The narrator knows what any casual observer knows, but no more. The narration is generally third person but one interesting case study is The Great Gatsby, where Nick Carraway could be considered an "effaced narrator."

I think you've got the idea, in between all of those descriptions, even if it's not quite coming together. Just trying a quick writing exercise in this manner will surely help you grasp it!